An old man takes his dog out on a rainy night. There are frogs and owls. The dog runs off into the graveyard and dies with a howl. The man follows and soon he is dead as well.

Soon after, the village doctor declares the man's death was due to a heart attack, not listening to the local white witch, Miss Olive Hawthorne, who declares the poor man died of fright. She has cast the runes and knows there is evil ahead for all of them.

Professor Gilbert Horner goes over preparations with a BBC TV crewman called Harry. Horner is performing an archaeological dig that night which is to be televised live. His target: the Devil's Hump, a mound not far from the small country Wiltshire town, Devil's End. He believes the mound holds treasures within the tomb of a Bronze Age warrior chief.

At UNIT HQ, Jo watches as the Doctor in a lab coat works on Bessie, his yellow roadster. She tells the Doctor it really is the dawning of the Age of Aquarius and about a TV program she's seen which is filled with hype about supernatural deviltry and witchcraft going on at Devil's Hump. The Doctor worries that he is wasting his time trying to turn her into a scientist. Everything has a scientific answer and explanation.

Jo watches as Bessie suddenly moves by herself and beeps her horn. Jo wonders if it was magic and asks Capt. Mike Yates, who has just arrived at the garage, if he believes in magic. He doesn't. The Doctor reveals that he just rigged up Bessie's solenoids to a radio control unit. No magic at all. Jo smiles and leaves, laughingly telling him she has had enough of him, calling him infuriating.

Yates tells the Doctor he will follow Jo as he is keen to watch the archaeological excavation on TV too. The Doctor takes off his lab jacket and chastises his friend, "Oh, not you too, Captain Yates." But when Mike mentions the name Devil's End, the Doctor has a memory stir of some kind and gets very serious about the TV program. He must now go and watch it, too.

TV host Alastair Fergus goes on and on about Devil's Hump and its mysterious background, mentioning 1793 when miners abandoned someone due to fear and ran back to Cornwall and also a disaster in 1939. At midnight - the Witching Hour - Horner will open up the mound and it will be broadcast live on BBC3. Tonight is Beltane, April 30, a festival night almost as renowned as Hallowe'en for its supernatural occurrences.

Olive arrives to protest the opening of the tomb, claiming she is a white witch and she has the talisman of Mercury. This is the night that the evil Prince is nigh. She wants the opening of the tomb stopped.

Watching her on TV, the Doctor becomes agitated, saying "That woman is absolutely right. We've got to stop that lunatic!"

He and Jo rush off to Devil's End in Bessie.

On TV, Fergus claims, "It seems that time is running in out in more ways than one." He announces that he will be back with the Passing Parade show at close to midnight.

In the local pub, Bert, the barman, and his townsfolk guests talk about whether or not goofy Olive has a point. There have been "queer goings on."

Outside, Olive talks to Police Constable Percy Groom. She says they must all be on their guard against coming evils. An unearthly wind rises up and as Olive turns to confront it with a spell of her own, Groom is taken over by some force. He lifts a rock up, intending to smash it down on her head. Her spells calm the wind and snap Groom out of it.

As Bessie heads for the small village, a vital road sign is turned around the wrong way by the strange wind, setting the Doctor and Jo off in the wrong direction. Someone or something doesn't want them to reach Devil's End.

Back at the village, Olive goes to see the vicar but finds Garvin, the verger. She wants to see Kevin Smallwood, the real vicar who supposedly left under mysterious circumstances in the middle of the night. He is not back and so agrees to see the replacement vicar even though she doesn't like him. Little does she know that this replacement, this Mr. Magister, is really the Master.

At the same time, the Brigadier is dressed up for a dinner party while Benton seems to have been stood up by his date or friends. He is stuck at the base with corned beef sandwiches and Yates, planning to watch Rugby on the TV.

The Master tells Olive that the "soul" is a dated concept and that he is more an existential realist. She scoffs at this. The Master takes his glasses off and tries, almost successfully, to hypnotize Olive. When he fails, he yells that she will listen to him. She walks off.

The Master waves for Garvin to get her.

It is now dark and Bessie is lost, the Doctor and Jo realize. The Doctor also realises that his assistant has been holding her map wrong side up. They start toward Devil's End, the correct way this time.

At the TV site near Devil's Hump, Alastair and Harry seem to verbally fight, both on edge, but they agree to apologize.

At UNIT, Benton watches the Rugby game.

The Doctor and Jo rush into the pub, the Doctor urgently trying to find someone who will give him directions to the Hump as quickly as possible and not getting any results. Bert tells him lazily that the place "will all be the same in 100 years time." There's no need to hurry. The Doctor assures him that it will be "no such thing."

Another man, older, mistakes the Doctor for one of the TV gents, what with the costume and the wig and all. He is the local Squire, named Montmorency Winstanley, The Doctor takes offense at the comments but Jo calms him. The Doctor has never heard such balderdash but the Squire tells him he is the one making all the fuss, calling him "old man." Jo gets him to tell them the directions - straight past the green, left fork, up the rise. The Doctor thanks him and he and Jo leave. The squire says, "What an extraordinary fellow."

One of the villagers, Tom Girton, a middle-aged man in a chequered jacket, left the pub while the Doctor was there, and he now reports to the Master the arrival of this white-haired man called the Doctor. The Master tells him to get ready - the ceremony will begin in a few minutes. As they talk a grey/white statue seems to watch them. This is Bok.

The Master puts a red cape on and descends to the catacombs under the church to perform a ceremony with 13 black-caped members of his coven. As the Master conjures, Bessie speeds toward the village. The Master makes his hand resemble Devil's horns, his pinkie and forefinger extended.

A tree falls outside, in front of Bessie, blocking the road so that the Doctor and Jo have to get out and run. Time is now running very short.

Professor Horner starts to remove the stone from the tomb as the TV show goes back on the air. It is midnight.

As they run, Jo trips and falls, preventing her from keeping up with the Doctor. The Doctor gets into the dig tent and down to the tomb but is too late to stop Horner from removing the stone from the tomb. The stone falls, releasing an icy terror from the opening within. Power knocks everyone down and downs the lights, shaking the ground. Snow blasts out at Horner and the Doctor. Dirt falls on them.

The Master is laughing as even his coven members fall. One masked member, Girton, points to Bok. The statue's eyes have lit up red... and the head turns at him.

Benton loses his bet to Yates and pays him. The score was 13 to nil.

Another soldier is with them watching the TV. They turn on BBC3 just in time to see Jo standing over the still form of the Doctor. "Doctor, no!" BBC3 goes blank and announces a temporary fault.

While Yates will try to contact the Brigadier, Benton gets on the phone to BBC3.

Others help Jo dig out the Doctor. The Master calls out to Azal, using a knife which will mark the appointed place and telling his assembled coven, "You have nothing to fear as long as you do the will of the Master."

Professor Horner is dead. Harry and Charlie help Jo, fearing the Doctor is dead, too. Jo asks them to help her get a doctor the TV men call for one.

Benton warns BBC3 if they are withholding info from him he will make them sorry. The Brigadier went somewhere after the dinner and no one knows where. Yates wants to go to Devil's End with Benton - in the Brigadier's helicopter!

The Doctor is brought to the pub where Jo cries on the Squire's shoulder as the Doctor is declared dead. He is like a solid block of ice. Yet, Dr. Reeves finds a pulse and calls for hot water bottles, exclaiming the Doctor must have the constitution of an ox. The Squire says, "He doesn't look all that tough."

Reeves checks the Doctor with his stethoscope, thinking at first there must be an echo bouncing off the bone for it sounds as if the patient has two hearts - one on each side.

The Squire tells Jo to be steady on. "Where there is life, there's hope, right?"

Jo phones up Yates and asks him to get down here as soon as possible. He will arrive in the helicopter at first light. The phone line is cut from the outside of the Devil's End pub.

The newspeople leave the area. The Constable is on night duty. He closes the gate at the dig and eats a sandwich. Two red eyes stare at him from the dig tent. Bok!

In one of the pub's upstairs bedrooms, Jo stands vigil over the Doctor's unconscious form. The Master looks at his watch and prays. The ground shakes in the morning. The Constable sees something huge and hears footsteps. He falls.

Benton and Yates are flying in the helicopter, both in flight jackets and plain clothes beneath. From the sky, they see enormous hoofprints.

Landing on the field, they examine the prints close up. Whatever made these must have been 30 feet tall and gone into the woods. Yates wants to get a move on something important. Benton asks Yates if he means breakfast. Yates says, "No, I don't. I mean Jo and the Doc."

Soon enough, they land outside the pub. Mike Yates tells Jo the Doctor is a "tough old bird, " and Jo tells him something devilish is in the air. Benton wants to make a recce of the area and Mike lets him. Jo asks him to be careful, and he promise he will. Yates realises he forgot to call the Brigadier.

In bed, the Brigadier gets a phone call from a corporal and finds he is the only one in bed. He yells, "My helicopter!" He calls for a car.

Benton goes outside to what seems like a peaceful, lovely, scenic village. That is until he hears calls for help from Olive who has been locked in a cupboard by Garvin, the verger. Benton lets her out and is called a knight errant. He tells her "all hell seems to be breaking loose." Olive says, "You know, Sergeant, you're exactly right."

When Garvin comes in upstairs, the pair hide down below the church. Olive finds the statue of the demon (Bok) is gone and pushes Benton roughly to keep him away from the evil marked signs on the floor, hurting his arm a bit. She tells Benton about the vicar, Magister, a leader of black magic. She also tells him that the last witchcraft act was repealed in 1951.

Garvin comes down with a rifle. Benton turns around but back kicks the rifle. Benton is thrown down but kicks Garvin away from him. The fight goes on but Benton is thrown over the markings on the floor and spasms out. Recovering his rifle, Garvin orders Olive to help Benton outside.

In the bedroom over the pub, Yates stands over the Doctor, "Doctor. Doctor, wake up!" Jo tells him the Doctor has been like that for hours.

Outside the ground shakes. Miss Hawthorne and Benton fall away from Garvin who shoots up at a giant, unseen beast. A burst of power and heat causes Garvin to vanish in a flame ball and a bush to burst into flames. Jo and Yates, in the bedroom, are thrown to the floor as the heat wave overcomes them. The Doctor suddenly springs up from the bed, "Eureka!"

The Master welcomes Azal.

On the road outside Devil's End, a baker drives his truck but stops when he hears a sound from the front of it. He gets out and watches as the front catches fire and the truck goes up in flames.

The Doctor stomps down the steps to the pub with both Jo and Yates fussing that he should rest. The heat wave revived him more fully. Mike asks him to tell them what is going on but the Doctor won't tell them yet until he is sure.

The bartender, Bert, comes in, then Miss Olive Hawthorne and Benton - a very heavy fellow indeed, she comments. Bert moves to get a doctor but the Doctor says, "It's all right I am a doctor." Jo grins.

The Doctor finds no bones broken on Benton and asks for hot water and sweet tea. The Doctor and Olive talk.

The Master gets a call from someone who is spying on the Doctor and his group.

Miss Hawthorne tells the Doctor and his friends that she saw the devil, 30 feet high and with horns. The Doctor has agreed with her up to now but this time she is "utterly mistaken." Olive tells him that Magister has used a black Sabbath mass to summon up the devil. Bert returns to the group. The Doctor figures out Magister is Latin for Master. Bert looks upset at this news.

The Brigadier and a soldier driving him in his car stop at the sight of the baker's truck. The baker explains what happened. By chance, the Brigadier points his crop forward and it suddenly bursts into flame.

The Brigadier's car is stopped near the sign for Devil's End. The Brigadier throws a small stick and discovers there is a heat barrier preventing them from going into that area. He wants to try to raise the Doctor.

At the same moment, the Doctor and Jo remove the tree blocking Bessie from Devil's Hump, get in Bessie and drive to the dig.

The Brigadier has managed to get Mike, "I see, Captain Yates, so the Doctor was frozen stiff at the barrow, and was then revived by a freak heat wave. Benton was beaten up by invisible forces and the local white witch claims to have seen the devil."

The Doctor and Jo arrive at the dig area. The Master seems to sense this and stands in front of a church sign in the church that reads "NOTHING IN MY HAND I BRING." The Master is frustrated the Doctor is still alive. He closes his eyes and hears a sound of footsteps - lighter ones this time, but steps with power.

Jo and the Doctor find the constable dead, crushed underneath the gate of the dig area. Jo will stick with the Doctor if he doesn't mind and if she is not in the way. The Doctor tells her not at all, in fact, he'd prefer her company. They go into the tent to the dig area.

Bok comes over the hill in broad daylight and makes his way toward the opening of the tent.

In the tent, the Doctor tells Jo that everyone in the whole world is in mortal danger. He finds a tiny spaceship in the tomb. It is the same shape as the tomb. Jo can't pick it up because it weighs 750 tons.

The Doctor calls out a strange language and holds out a trowel made of iron to ward off Bok, despite the Master's claims to Bok that it cannot harm him.

Bok is recalled. When Jo asks what it was the Doctor recited, he tells her it was an old Venusian lullaby. Roughly translated, the first line means, "Close your eyes, my darling, well three of them at least." Jo laughs, "Oh, Doctor." The Doctor admits that thing took him completely by surprise.

The Master tells Winstanley to act like the squire. The Master is sick of democracy, liberty, and freedom. He hypnotizes Winstanley, "I am the Master. I control the power which can save this world." He controls the forces at the dig, and as proof he offers up a strong gust of wind.

Benton and Miss Hawthorne bring in a load of occult books for the Doctor's use at the pub. The Doctor tells them the force field around town is a psionic one. Miss Hawthorne and the Doctor disagree. She thinks it is magic and he calls the force in Devil's End science. When Jo joins in and starts talking logically, the Doctor smiles. He thinks he will turn her into a scientist after all.

Yates gets a call from the Brigadier who cannot get past the heat barrier which springs from ten miles all around the church. An RAF plane has dropped a test canister over the top and found that the heat barrier rises with a roof about one mile high at apogee. The Doctor tells him they are locked in. The Brigadier is then hung up on and can't get Yates or the Doctor. "Typical."

Yates, in the pub, asks the Doctor to explain the "wider issues" involved. The Doctor uses the books to show them Croue, a god with horns worshipped in Egypt; a Hindu demon with horns; and the devil. Yates doesn't get it. The Doctor says, "That's because I haven't finished."

He tells them that the thing Miss Hawthorne saw is a creature from another world. Benton asks, "You mean like the Axons and the Cybermen?" The Doctor confirms this but says that these Dæmons - from the planet Dæmos - are a great deal older and much more dangerous! They came to Earth in tiny ships from 60,000 light years away. Jo helps the Doctor explain this part to the others: the Dæmons came to earth over 1,000,000 years ago.

The Squire is to gather the townspeople for the Master.

At small size, the Dæmons' ship is 15 inches. At full size, it is 200 feet long and 30 feet across but they have the power to diminish it. The Doctor tries to tell his friends that the heat and the cold they have been experiencing is a result of the ship thing loses mass or getting it back E=MC².

Yates now understands, "I see. So all we have to deal with is a creature which can be too small to be seen or 30 feet tall, can incinerate you or freeze you to death, turn stone images into homicidal monsters, and looks like the devil." The Doctor tells them the Dæmons have helped homo sapiens kick out Neanderthal Man in the past, helped the Industrial Revolution, the Greeks, the Renaissance, and at other times in history.

Jo asks what that "jazz" about witchcraft is. He says it is left over remnants of their sciences, not black magic. The Dæmons are not evil, just amoral. They think of the Earth as their lab experiment. The Master's link with them is dangerous since he is summoning them and this could result in the Dæmons throwing away or disposing of its lab experiment - the whole world.

The Master, as Magister, addresses the townspeople and tells them individual things they have been doing to cheat each other. Mr. Thorpe pads the grocery bills. Charlie has not done the post office books correctly or on time. Mr. Grendel's wife is at his sisters and the Master implies it is due to something Grendel did wrong. The Master takes his glasses off and demands they listen to him.

The third call of the Master to the Dæmon may be the time their fate is decided by the creature. Right now, it is so small it is practically invisible.

The Brigadier calls Yates, readying an RAF command to attack the energy barrier. The Doctor takes the radio and tells him not to do any such thing: it will only strengthen the barrier and call forth the most hostile reprisals from the aliens.

The Brigadier has a mobile HQ with a New Mark 4 condenser unit aboard. The Doctor wants his technician fellow Sergeant Osgood to build a diathermic energy exchanger. He tells them to use the EHF wide band width variable phase oscillator with negative feedback circuit tuned to the frequency of an air molecule at the temperature of the heat barrier. Of course, they do not know what he is talking about so he will have to come and explain it on the site.

Jo says the idea of blowing things up is idiotic but the Doctor tells her the Brigadier is coping with an impossible situation and he is her superior. She should show him some respect.

A spy for the Master leaves. This is Tom Girton.

The Master tells the other townspeople they will bend to his will in submission and obedience. The Squire asks what happened to their ruling together. The others seem none too keen to follow him.

The Master gets more malicious, his glasses off again, and calls them dust beneath his feet, threatening to destroy them. When the Squire tries to leave and take others with him, the Master summons Bok to destroy him with a bolt of fire from his finger tip. After the Squire vanishes into nothing, The Master tells the others to enjoy their May Day today.

Girton gets in the UNIT helicopter. Mike Yates rushes out to stop him and is beaten up. The man seems not to feel Mike's punches at all. Girton beats Mike to the ground and takes off. Mike fires his gun at the helicopter but to no avail.

Mike gets onto a motorcycle and rushes to warn the Doctor and Jo who are in Bessie en route to the Brigadier near the barrier. They already see the helicopter which has buzzed close to them at least twice already. Girton is flying the helicopter like a man possessed, but expertly. Mike wants to draw him off but the Doctor warns Mike off, "Keep away. It's me he's after." Yates drives away from the Doctor but tries shooting at the helicopter again.

As the helicopter dives at the Doctor he says, "Hang on, Jo, we're in for a bumpy ride!" He drives Bessie straight at the barrier but turns at the last moment, warning Jo to hold on tight. The helicopter hits the barrier and blows up, something the Doctor's face didn't read as if he wanted to happen.

Jo falls out of Bessie and gets a nasty bump on the head. Mike will take her back to the pub in Bessie. The Doctor takes the motorcycle and go the Brigadier, who, he tells Mike is probably "bursting a blood vessel by now."

The Master makes Bok go back to his cavern hold.

The Brigadier complains about 20,000 pounds of UNIT money up in smoke. The Doctor tells him he has the mind of an accountant. The Brigadier has tried wood, rock, and four inch armour plates to get into or across the barrier. The Doctor asks him to use a cable to connect to the high tension wires at the electric towers off in the distance. This will give them 10,000 volts.

Sergeant Osgood will assemble the device, following the Doctor's instructions, which Osgood claims are impossible. The Doctor notes that the bumble bee being able to fly is impossible according to the laws of aerodynamics.

By himself, the Master starts his summoning of the main Dæmon creature - Azal.

Yates and Reeves help Jo to the bedroom over the pub. Jo murmurs about the Master. Suddenly the room shakes. The heat wave starts again.

The Master uses an iron candle holder to hold off Azal but the creature is not impressed.

At the pub, Jo sneaks off in a delirium and heads for the cabin, going down a ladder from the second story after climbing out her bedroom window.

Olive Hawthorne and Benton stop Yates from going to find the Doctor who, at the moment, is suggesting that Osgood "reverse the polarity." The Doctor tells the Brigadier the device should be ready by next Christmas some time, referring to Osgood's slow progress. The Brigadier tells a bemused Osgood, "The Doctor knows what he's doing." Then the Brigadier gets closer to the Doctor, who is still on the other side of the force barrier and asks, "Do you know what you're doing?" The Doctor answers him, "My dear chap, I can't wait to find out."

Two giant hooves attached to the Dæmon stand in front of the Master, who feels he is quickly losing control. In any event, he tells the alien he wants power and wants the Dæmon to make him this world's leader. Azal thinks there is another like the Master here, both of them superior to the humans. He tells the Master the Doctor lives.

Azal wants to talk to this Doctor to see if he is worthy to have power over Earth. Azal also warns the Master, "I am not your slave and you are not immortal." The Master claims his right and Azal says he will consider making the Master leader of the Earth... if Azal lets the planet continue to exist.

Azal tells the Master he will appear only once more - the third time - and then will decide if he should destroy the Earth as one of his race's failures, telling the Master to "remember Atlantis." He also tells the Master he is the last of his kind and that this planet smells of failure. He asks if the Master still wishes him to reappear. The Master does.

The creature goes back into hibernation with a burst of heat and the Master laughs. As it does, Jo seems to be held by a tree, falling into its vines.

At the barrier perimeter, Osgood tells the Doctor that the feedback circuit cannot be in phase with the pulse generator and vice versa. The Doctor exclaims that is the whole point and begins to explain it again.

Yates find Jo out of her room and calls her a little idiot while Olive Hawthorne and Benton share a drink.

The Master tells a henchman, Bert, that "The Doctor's been in my way far too long." The next time he summons up Azal he will be smarter... and not do it alone. He will need the coven present, needing all the power he can muster to control the creature. He admits he was foolish to do it alone the second time. In the church graveyard, Mike hides as Bert leaves in a car. Mike then goes into the church.

Elsewhere, at another entrance to the church catacombs, Jo falls out of the tree of vines that seemed to be holding her.

The Doctor tells Osgood, back at the barrier, that his plan is as simple as Einstein's theory of relativity. When the Doctor leave on the motorbike, the Brigadier stares after him and tells Osgood, "You know Sergeant, I sometimes wished I worked in a bank."

Jo sneaks away from the ivy vines and is wary to keep away from them as she finds a way into the church catacombs. In the catacombs, Jo is scared by the inactive Bok sitting in his alcove. Mike finds her there and tells her the place is alive with booby traps. He demonstrates by tossing a book into the magic markings on the floor. It is ripped to shreds. He reminds her what happened to Benton when he stood on the markings.

The traps are spells, elementals or force fields, call them what she will, he tells her. They take cover behind a wheel as the Master and his coven reconvene.

The Doctor cycles back but Bert, from the bushes, shoots at him. The Doctor falls with the motorbike but gets up and runs. Bert shoots at him but misses due to the surprise of finding the Doctor so mobile after such a skidding crash.

Back at the pub, Benton is worried. Olive brings in some tea, telling him he has to master the art of waiting as she has. The Doctor will either come back or won't. She refuses to worry about any of it.

At the UNIT truck and the alien barrier, Osgood is fascinated by the Doctor's devices and tests. He will run one more test and tells the questioning Brigadier it will take one more minute. The device suddenly blows up in his face and he tells the Brigadier ruefully that it will now take half an hour at least!

Bert reports back to the Master, who is not surprised the Doctor got away again.

Benton reports to the Brigadier that the Doctor has not returned. The Brigadier notes that the Doctor left 40 minutes ago and comments that he probably piled up that wretched motorbike. After the talk, Olive wants to go look for the Doctor but Benton orders her not to and tells her she will do as she is told. She does. The pair of them, from the pub, hear May Day revels starting.

Outside, the May Day Morris Dancers parade through the streets. A mother pulls her little girl inside. The Doctor turns up and tries to avoid their frivolous May Day banter as they surround him and begin hitting him with their sticks. He tells them any other time he would join in with them.

The hitting becomes more violent and the male revellers take the Doctor to Bert near the Maypole. Bert is dressed in paper shreds and has a revolver pointed at the Doctor's head. The Doctor is tied to the pole.

While this is happening, one of the men attacks Benton in the pub. They have a huge fight which ends with Olive hitting the man over the head with her pocket book which has her "retinue" it: her heavy crystal ball. She tells Benton the people in this town are not wicked - well most of them. She knows them; they would never do such things and would certainly not burn the Doctor at the pole. She wants to go out and explain the situation to them.

Outside, Bert tells the people that "Mr. Magister will care for you." Bert calls the Doctor a black witch and tells them "thou shall not suffer a witch to live." The Doctor asks him if he is completely out of his mind.

The Master, in the catacomb, starts the last ceremony to summon Azal. The coven is there and Bok's eyes light up once more.

Olive has a plan. With Benton hidden, she runs out to the pole and stops the people from burning the Doctor, declaring him to be Quiquaequod, a great White Wizard, who can bring them peace and joy. She bluffs her way through this, knowing the people did not listen to her in the first place and now they are in the power of the Magister.

She tells them - and the confused Doctor - that he has to prove his power and he can. She bluffs to him that he should make the lamp on a post shatter. Using a high powered rifle, Benton shoots at it. A similar bluff makes them think the Doctor turned the weather vane on top the church tower.

The others fall for this trickery but Bert will not. He takes the torch from Thorpe and is about to burn the Doctor to death himself. Benton shoots the torch out of Bert's hand. The Doctor, less questioningly and more authoritatively but calmly asks Olive, his "Daughter of Light", to untie him.

Bert once more gets his small gun and aims at the Doctor. The Doctor warns him not to. The Doctor makes his familiar spirit Bessie move by itself at Bert. It knocks the man over. Benton comes running and asks how he did it. The Doctor smiles, "Elemental, my dear Benton." Before the Doctor can explain, Bert tries to get away. Benton jumps him and subdues him, "Oh no you don't. We've all got a date with the Master!"

The Brigadier pushes Osgood to finish the device in five minutes.

In the church cellar, Yates shoots at Bok who fires back at him. Yates ducks from the bolts but has to surrender and puts his hands up. The Master calls that sensible.

Outside, the Doctor tells the townspeople that the world is facing the greatest danger it has ever known. He also offers them the truth even though Miss Hawthorne didn't want him to. While Bert still claims the Master is the truth, the Doctor shows them how he rigged up Bessie with a remote control and honks the horn. He explains the Master is using nothing but science, too. Violent emotions from humans are used to gain psychokinetic energy channelled for the Master's own purpose. The Sabbath and rituals are needed to control the psi forces. Benton asks the Doctor why they don't just go and sort out this Dæmon fellow. The Doctor asks how.

Jo has been dressed up in a sacrificial gown and put near the stone slab. She is held by two of the coven. Yates is tied up with his hands behind his back but he manages to get out the door and runs, calling for the Doctor, explaining about Jo when he finds him.

Benton unties Yates while the Doctor calls the Brigadier. The Brigadier orders Osgood that they are going in now. The Brigadier is told by the Doctor to have some men keep watch at the barrow.

In the cavern, the Master tells Jo, "I'm sorry, Miss Grant but you are to be a sacrifice to a noble cause."

Outside, the Doctor tells the townspeople to split up. Bok appears before anyone can get near the church. This gives Bert his chance to get free of the men holding him. He pleads with Bok to let him enter but Bok shoots him with a bolt and Bert vanishes. The Doctor holds back Benton and Mike, telling them that committing suicide won't help Jo. He needs that booster device.

The Brigadier calls him on radio, "We're coming through, Doctor, over and out."

A young man holding Jo tries to tell the Master this is not right.

The Brigadier and almost all the UNIT men drive through the open area in the heat barrier. Osgood is driven in last by Jenkins. Just as he drives through, the machine overheats and overloads. Osgood tries to save it but the Brigadier orders him and the men down. The device blows up. The Brigadier reports this to the Doctor.

The Doctor runs past Bok, who is weakened from the brief time the machine was inside the heat barrier, as was Azal. The Doctor manages to get inside just as the outside of the door is blasted by Bok. He goes down to the Master who was expecting him. The Doctor tells Jo he is very glad to see her. The Master mocks him: "How very touching."

The Brigadier joins Yates outside the church and asks what Bok is, "an ornament of some kind?" Yates demonstrates by tossing a brick in the air. Bok blasts it. The Brigadier then calls Jenkins, who hurries over, "Chap with wings there. Five rounds rapid." The gunfire does no good.

The Doctor tells the Master he knew he was dead the moment he came through the door so he had better be careful. The Doctor has nothing to lose now. The Master insists that Azal destroy the Doctor, whom the Master calls a meddler and a fool. Azal knows the Doctor is not a fool and, at the Doctor's request to have Jo released, shoots electric at the men holding her. They fall, stunned. Jo runs to the Doctor.

The Doctor tells Azal to just leave, but Azal brushes this aside, telling him he is being overbold. The Doctor tries to bluff that the machine which weakened Azal was destroyed but that he has another. Azal knows there was but one and asks the Doctor why he lied. He is not prone to lies. Jo protests as the Master continues to try to get Azal to kill the Doctor.

Outside, Yates orders Benton to get the bazookas.

Azal tells the Master the one in command is Azal! He does not obey the Master; the time has come for his awakening. The Master wants Azal's ultimate power given to him and he shall lead this experimental people into his rule for their own good. The Doctor talks to himself, wondering if he heard these same lines from Adolf Hitler or Genghis Khan. The Doctor tells Azal to just go. He and his kind have interfered with Earth enough.

Azal counters by telling him his people brought man knowledge but the Doctor tells him that man can now blow up his world and poisons the water and the air. Azal takes this to mean man is a failure. The Master continues to try, telling Azal he will force mankind to learn if he is placed in charge. Azal determines that he will pass on his power...to the Doctor! The Doctor protests now, "No! No, I don't want it!"

Outside, Bok incinerates a UNIT soldier into nothingness. Benton arrives and fires a bazooka at it, blowing it to bits. But the pieces come together and Bok reforms.

The Doctor, in the cavern, is telling Azal to give man a chance to grow up. Azal then decides he will give his power to the Master after all. And since the Doctor has been a disruptive force, he will have to be eliminated. Azal fires electric from his fingertip at the Doctor, who starts to slump over from it. Jo throws herself in front of the Doctor, "No! No, he's a good man. Kill me, not him!"

This selfless action throws Azal into a fit. It does not relate he yells and holds his head. This data does not fit. He screams at them to all leave him alone. A Dæmon must die alone. They run and the ground shakes as he stamps his hooves.

Outside, the Brigadier taps his stick onto Bok's head. The thing has just sat down in its original position and become a stone statue again. Just then, the Doctor, Jo, and the black-garbed coven come running out of the church, the Doctor yelling, "Run for it, Brigadier!"

With everyone outside, even the Master, the church explodes until nothing is left of it. Benton has a gun on the Master. The Doctor explains to everyone that Jo's self-sacrifice, a totally irrational and illogical move, drove Azal insane. He couldn't take it and all his power was turned against himself. They hear more blasts. A UNIT officer calls from the barrow saying that the ship has destroyed itself. Some kind of automatic self-destruct, the Doctor figures. The barrier is gone as well.

The Master tosses his cape over Benton's head and runs for Bessie. The sergeant shoots at him but misses. The Brigadier shoots too, but as the Master drives off in Bessie, the Doctor warns him, "Stop firing, you'll damage Bessie!" The Brigadier doesn't want the Master to get away. The Doctor smiles as Bessie brings the Master back to them.

The evil Master is soon surrounded by UNIT men with drawn guns. The Brigadier orders him taken to maximum security prison. The Doctor asks them to look after him; he wants to deal with him later. The Master calls him an optimist, but the Doctor takes that as a compliment. Standing in the back of the jeep, many UNIT men seated on either side of him with guns, the Master is driven away. Benton keeps a gun trained on him until the jeep leaves the area. The town boos the Master.

Olive Hawthorne rejoices in the sound of birds returning and the sweet smell of flowers over sulphur. She tells them the Earth is born anew as it is each May Day. Olive takes Benton to do the May Pole Dance while Jo takes the Doctor, who tells her to get out of that ridiculous gown. Yates asks the Brigadier to dance but the Brigadier would rather have a pint to drink at the pub, Cloven Hoof.