Some time later Clyde, Luke and Rani arrive at the local theatre to see Martin Trueman’s latest show. Clyde is sceptical of horoscopes, but Rani challenges his disbelief. She reveals she is an Aries, and asks the boys what their signs are. Clyde’s is Gemini, but Luke does not have one – he was not born.

The three friends are met by Cheryl, Mr Trueman’s assistant, who asks them to put down their names and star signs on a piece of paper. Luke is not sure what to write, but he is saved when Sarah Jane arrives with Gita and Haresh, Rani’s parents, who are also there to watch the show.

As the show begins, Cheryl’s partner Stewart arrives and confronts his wife. He asks her to come home but she insists she must stay with Martin. Stewart claims something has changed since she met Martin, but she denies it and orders him to go, which he does so, begrudgingly. Having overseen this exchange, Sarah laments the fact she cannot go anywhere without something odd occurring.

Sat in the auditorium, the friends watch as the show begins. Now dressed in a smart white suit, Mr Trueman appears, accompanied on stage by a large prop displaying each of the twelve star signs. He talks to the audience about astronomy and astrology, and how the stars hold certain secrets. He demonstrates by picking three birthdays – one of which is Clyde’s, and forces the people to whom they respond to stand up and sit down in quick succession, which Clyde finds somewhat embarrassing. He asks Sarah how this was done, and she claims it is simply the power of suggestion.

Using the information gained by the cards collected by Cheryl, Trueman then begins picking people out from the audience and predicting facts about them. One of these people is Rani – whom he correctly predicts has just moved house, and whom has just found a new outlook on life. The next person is Sarah, a Taurus, whom he claims was born under a special star. His predictions are startling indeed.

“Some years ago you travelled far and wide and, oh, the things you have seen. And there was a man, a very special man…it wasn’t a romance…it was something much more than that. He taught you so much. There was laughter, and adventure, and you prayed your time with him would never, never end. A man with no name, a scientist? No, a doctor, the Doctor.”

Sarah confirms these predictions and challenges Trueman’s abilities, but he has not finished yet, upon Sarah’s request he looks to the future.

“If you want but, oh, I’m afraid Saturn is transiting Taurus. You have fought many battles in your life, you’re about to fight another, but this time it will be different. This time Sarah Jane…you lose.”

After the show Gita and Haresh discuss Mr Trueman’s abilities before Rani hurries them away. Sarah, Luke and Clyde are unsettled by Trueman’s knowledge of the Doctor, but Sarah insists a scan she secretly conducted with her special watch has confirmed Truman is human.

Backstage Trueman tells Cheryl that the night’s show was the last, they have served their purpose but Martin has to take on a bigger opportunity…at that moment Lisa Trotter, a reporter on the Paranormal Channel, enters the room and offers Martin an interview on her show the next day. He accepts, claiming he wants to get his message across to as many people as possible.

Calling Mr Smith; Sarah, Luke and Clyde ask about alien activity around the theatre, but nothing is found. Sarah insists there must be some cause for Trueman’s astrological ability – which is theoretically impossible – and claims Trueman must be using a biodamper – a device used to hide alien activity.

Back at his home, Martin tells Cheryl that in the greater scheme of the universe, the ancient lights are aligned upon him, he is truly special, and the broadcast tomorrow will confirm this. He predicts that Sarah Jane Smith will try to stop him but he claims destiny will take over, and she will fail.

The next day Sarah tells Luke she is going to visit Trueman, and she finds her son is somewhat upset at not having a star sign. She claims she can give him a birthday but he is not so enthusiastic, it is just another sign that he is different – that he has not, does not, and will not ever be able to live a normal life. Sarah insists he will cope, and after comforting him, leaves to see Trueman. Outside the house she is met by Rani, whom she invites along.

Whilst they are gone Luke talks to Mr Smith about astrology, and he discovers it stretches back far beyond Earth history to many other alien worlds with their own zodiac charts.

Sarah and Rani, meanwhile, visit Trueman and Cheryl and they talk about his sudden rise to fame. Again Trueman begins to goad Sarah by talking of the Doctor, but refuses to explain how he is able to know about him. He then sees Sarah scanning with her watch and claims she will find nothing. Soon a battle of words begins between the two of them, and again Trueman claims Sarah’s luck will change. She and Rani then hurry away, but not before Trueman has threatened them with a special power – the ability to shoot concentrated electricity from his fingers, which he uses to zap Rani’s jacket.

Watching them go, Cheryl claims they will not come back, but Trueman knows this to be false, they will interfere again. However, with the two of them busy working on the broadcast, he claims they will need someone else to deal with Sarah and Rani…they choose Clyde, who is across town talking on his mobile phone. Suddenly Trueman and Cheryl appear. Just like the previous night at the theatre, Trueman starts giving him orders…which he begins to obey.

Arriving back at the attic, Sarah and Rani tell Luke and Mr Smith about Trueman. However, when Mr Smith inspects Rani’s singed jacket, he claims the source of the burn does not exist – according to his sensors the jacket has been burned by nothing.

Clyde awakens in Trueman’s house, when Rani calls his mobile phone. Trueman cancels the call and turns to Clyde, telling him that he will soon join his inner circle. He places a hand on his shoulder and zaps him with electrical energy.

In the attic, Rani begins to deduce that the energy that burned her jacket must not have come from Earth, and therefore is not detectable. However, Sarah insists that any alien energy must come from their universe, which is bound by the same basic laws of physics. Luke realises that the energy must therefore come from a different universe…

As Clyde, now under Trueman’s control, departs the house, Martin tells Cheryl that they must prepare for the broadcast. Back on Bannerman Road, Luke theorises that astrology, being something that predates Earth history, may in fact be an echo from something that existed before their universe began, in another universe that was replaced by their own following the big bang. The Ancient Lights controlling Trueman were forged under a different set of physical principles.

Sarah questions why the Ancient Lights chose to possess Trueman, and Mr Smith claims this is part of an ancient astrological equation. Trueman’s birth chart represents part of this configuration of stars, and it is therefore important the ancient lights took control of him, for he will help them achieve whatever it is they are seeking.

Mr Smith detects Trueman’s broadcast. He shows it to Sarah, Luke and Clyde, who watch as Trueman talks with Lisa Trotter. Mr Smith claims this transmission is being broadcast on every channel around the world. Sure enough, Gita and Haresh find themselves watching it over the road.

Back at the theatre, where the transmission is being conducted, Trueman and Cheryl knock the entire television crew out and take over the running of the cameras. Trueman claims that today is a very important day. However, before he begins he talks indirectly to Sarah, telling her to stop interfering or people will be hurt.

Sarah Jane tries to appeal to Clyde’s suppressed human nature, but he maintains that the group must stay still and silent.

Trueman continues his broadcast, addressing all people with the star sign Gemini, including Gita. She watches and listens to Trueman’s words, then is suddenly overcome by some invisible force. Obeying Trueman’s commands, she begins walking out of the house, much to the disbelief of her husband Haresh.

Up in the attic, Sarah continues to try and reclaim Clyde’s mind, albeit unsuccessfully. Using Trueman’s orders for her death as an excuse to let Luke and Rani leave safely, Sarah convinces them to leave. All the while Trueman continues to urge people to join with each other and form circles by holding people’s hands.

As more and more people begin walking from their homes, Trueman calls upon the star sign Cancer to join those under Gemini, and the march across the world continues. Rani can do nothing to stop her mother, whilst in the attic Sarah and Luke, who refuses to leave, confront Clyde once more.

Sarah tries to push Clyde to the point of destroying her but he doesn’t. After a friendly hand on his shoulder from Luke, he appears to be relinquished by Trueman’s force, and collapses, moments after Rani returns to give news of her possessed mother.

Mr Smith relays news reports from all over the world – people are beginning to march out of their homes, under Trueman’s command. Soon more join them as the star sign Leo is brought under Trueman’s influence. Rani begins to worry what can be done to save a hypnotised world, and Sarah and Luke theorise Clyde may be the key – he is the only one to break the spell. However, Clyde has no memory of what has happened. Sarah realises that she must have freed Clyde by pushing him over the edge (ordering him to kill her) and decides she must do the same to Trueman to break the influence that is holding him. As the group go down to the car Luke claims they must also stop Trueman’s broadcast by cutting off the power supply in the theatre.

Over at the theatre, all those who are Gemini step inside to join Trueman, for they are his inner circle. This includes Gita. Haresh looks on as some of the other hypnotised people begin to form a circle around the building, with which to protect their leader. Next the children on Libra join the possessed hoards, and then Scorpio.

Soon Sarah and her friends arrive at the theatre, just as the children of Sagittarius are brought under Trueman’s control. Clyde decides to use his position as a Gemini to bluff his way through the circle outside the theatre, and pretends to be possessed. He claims he is of the inner circle and that the others are his prisoners. Eventually he gains entrance, just as Capricorn is taken over.

Mr Trueman senses Clyde has entered the building and that the control held over him has broken. Sure enough he and the others are one their way. Luke and Rani run to find the electricity supply to turn it off whilst Sarah and Clyde are confronted by Cheryl, who has been sent by Trueman. They are taken to the main auditorium, where Trueman orders them to kneel upon the stage. He then reveals the intentions of the Ancient Lights – to unlock the power of the minds of all those captured and then use it to transmit the signal to the rest of the universe – giving the Ancient Lights complete control of the cosmos.

Sarah tries to appeal to Trueman’s human side but he is not so easily convinced – any appeal to his better nature is futile, the part of Trueman that is human, the part that lived a life of being pushed around, is enjoying the control and the power it now has at its command. Born at exactly the right time for the Ancient Lights to take over him, Trueman finally has a purpose.

Soon a rumbling is heard outside – the conjunction is starting. Trueman then begins to call upon the children of Pisces, and Clyde realises that Sarah’s plan has failed – just as Trueman predicted the previous night.

Suddenly a shaft of red light falls from the sky and hits the theatre, emerging on the stage, engulfing Trueman. Elsewhere in the building, Rani and Luke have found the main cut-off switch, which Rani discovers is electrified. However, when Trueman brings Aries under his control, she is forced to leave for the stage. When Luke tries to deactivate the switch he is not affected by its shield, and is able to cancel the power and stop the transmission.

Sarah and Clyde rejoice, but Trueman remains in control, still bathed in the red column of light. Rani walks onto the stage as Trueman claims stopping the broadcast will not stop the Ancient Lights, which are now too powerful. He tells Sarah only her star sign, Taurus, is yet to be harvested, but when it is she too will fall under his control.

Luke runs on stage but Trueman claims he is too late to act. However, Luke has realised the truth about why Clyde was freed and why he was able to use the switch when Rani could not – it was his touch. He runs forward and uses his power to break the inner circle around Trueman, which in turns releases the people standing outside the theatre. He explains that as he has no birthday, he is not affected by astrology and as such can break the link forged by the Ancient Lights, thereby thwarting their plan.

Trueman claims the constellations are beginning to move – soon the Ancient Lights, and he, will be lost forever. Sarah begs him to release the light but he refuses to return to being nothing, and instead allows himself to be scattered to dust by the decaying lights, which zoom away from Earth once the alignment of the constellations is broken and all of Earth is freed.

That night Rani returns home to find the house empty. She turns on the television and watches the fallout of Truman’s broadcast, which is believed to be a malfunctioning publicity stunt. Now everyone is released – including Cheryl, who has returned to her husband. Soon Gita and Haresh, both safe, return home and the family is reunited.