Engineer Robar is complaining about a fault in the system to the captain, old friend Lisa Deranne, but nothing shows up on the checks. Robar claims that it comes and goes. Lise leaves him to make a full power check. This means they’ll have to shut down the main drive. Lisa takes the opportunity to put the crew through their first sail drill. (Robar: “They’ll like that.”)

The crew, who are also the financial backers, consists of Zorelle, a self-centered fashion magnate; Mari, the daughter of the president of Valeria; her boyfriend Nikos, the son of Valeria’s leading industrialist; and Kurt a shady self-made man. Lounging in the crew quarters, Zorelle complains about the lack of respect that Lisa has shown them. This is an old argument, as Kurt placidly points out that despite all the money they’ve put into this venture; it would be meaningless without Lisa. Then he points out that while Lisa earned her reputation, Zorelle inherited hers, putting her on the defensive. Mari can’t help but throw her own two cents in, further irritating Zorelle. Kurt states the best way to go about getting rich is to start with nothing and work your way up. Nikos and Mari ask how he came into his money. Kurt is vague and evasive with his answers.

Aboard the War Wheel, the ruthlessly efficient Commander Steg is informed by his thuggish, battle scarred subordinate, Lieutenant Vorn that they are approaching their target. Steg orders Vorn to select a boarding party and inform the admiral of their intentions. Steg finishes recharging and prepares for battle.

Lisa arrives just as Zorelle complains that she doesn’t even wear the captain’s uniform jacket she designed. Lisa cheekily puts it on before entering the crew quarters to fill them in on their power troubles. Mari asks why they just don’t use the solar sails and Lisa explains that the best thing solar sails do is break down. Captain Deranne then tells them they’ll be doing their first sail drill.

On the Sail Bridge, Lisa gives a speech about the importance of a quick start. The crew is now clad in jump suits with the Tiger Moth logo with virtual reality goggles and gloves to operate the sails. Mari has doctored her uniform slightly, while Zorelle vamps her way onto the deck in her own specially designed uniform.

When they finish their drill, Lisa is far from impressed. “More like an arthritic Algolian dung beetle, than a Tiger Moth.” She continues to berate the crew for its slow reaction time, while Robar watches amusedly from the flight deck.

Unknown to the Tiger Moth crew the Sontaran War Wheel approaches. The War Wheel fires a warning shot, resulting in minor sail damage.

Lisa returns to the bridge leaving the others on the sail deck.

Robar tries to establish a com link, but it keeps fading. When Lisa arrives he manages to establish a link. Commander Steg informs her that they are about to be boarded and not to resist or be destroyed.

Lisa retracts the solar sails to avoid more damage, while Robar keeps busy by going down to the power room to check the drive units. Lisa then informs the crew of the situation.

A shuttle disembarks from the War Wheel while it proceeds to the next intervention point. Lisa monitors the shuttle as it docks with the Tiger Moth.

On the sail deck, Zorelle gets fed up with waiting and goes to deal with the situation herself. Mari, Nikos and a very reluctant Kurt follow.

At the air lock, Nikos pulls out a gun, but Kurt makes him put it away. A small smoking, sphere rolls down the corridor and explodes, but not before Kurt shouts a warning. He absorbs the full brunt of the explosion and collapses on the floor. The others flee as the Sontarans storm the ship.

The crew is picked off one by one. Nikos manages to shoot one, but it doesn’t seem to have any effect, as he is stunned in return. Mari and Zorelle are stunned as well. When Lieutenant Vorn confronts Captain Deranne, she demands an explanation for their actions. Vorn responds by shooting her as well.

Commander Steg reviews the crew manifest and finds that one crewmember is missing – Robar. It takes some explaining on the commander’s part, but the somewhat thick Lt. Vorn eventually sends a trooper to search the engine room.

Robar, meanwhile, completely oblivious to what has happened, is finishing up his check of the power units. Inside one he finds the Rutan spy the Sontarans are looking for. Much to his misfortune, as it kills the engineer.

The crew recovers in their sleeping quarters. Kurt recovers first (he has been stunned before, possibly proving some of the stories about his earlier years). Lisa recovers next. Kurt gives her something to drink to ease her aching head. She asks why he didn’t revive the others. “They’d only start moaning.” As if to prove a point, Zorelle starts moaning. Nikos awakens and goes to Mari. Kurt gives her a drink, mainly just to shut up a panicky Nikos. They’ll suffer from a dry throat and a sore head but nothing else. Zorelle continues moaning theatrically, but nobody takes any notice.

Kurt and Lisa talk about what is happening. Lisa at first thinks it’s piracy, but Kurt thinks it feels more military. Lisa gets up to find out what’s going on only to find a Sontaran trooper on the other side of the door. They’re not going anywhere.

The Sontaran trooper sent to find Robar, instead finds the Rutan disguised as the engineer. Not realizing it this, the Rutan the trooper allows it to get close enough to kill the trooper with a massive electrical shock.

Vorn enters the sleeping quarters and orders everyone to stand. At first only Kurt complies. He convinces Lisa to do the same. There is no point in getting killed now. Zorelle, Mari and Nikos protest their treatment and Vorn’s actions, but he ignores them and tells them to move.

Outside the sleeping quarters, they meet Commander Steg. Without their helmets Kurt recognizes them as Sontarans. Steg questions how he knows their race. Kurt says only by reputation. Vorn thinks this means he’s heard of their glorious empire. But that’s not the reputation he’s heard of.

Steg wants to know why the ship is equipped with solar sails. It would be much more efficient to use the power drive. Lisa and Zorelle try to explain the concept of a race but neither Steg nor Vorn understand. When Lisa asks what Sontarans do to challenge themselves he replies enthusiastically, “War”.

In the engine room the Rutan disguises itself as a trooper to avoid detection from another trooper. When that trooper has left, it reverts back to its natural form and slips away.

Steg explains why he’s here. He is looking for an enemy of his people, which Kurt knows is a Rutan. When Steg attempt to pry what Kurt knows about the Rutan, Kurt states that all he knows is that the Sontarans are at war with them. The Sontarans recently boarded and searched the Tiger Moth’s last port of call, Space Station Alpha. The Rutan wasn’t there, so they are now going to search every ship that has recently past through the station. Space Station Alpha is one of the most heavily used stations in the system, hundreds of ships past through there all the time. Zorelle is stunned that the Sontarans intend to search every single one. Steg has no interest in the crew’s survival but has no reason to harm them. He claims that once he’s through here he and his troopers will leave.

Nikos protests that Steg’s actions are a violation of the Tri-System Alliance, but Vorn loudly states that Sontarans do not concern themselves with the laws of primitives.

Steg becomes intrigued when he discovers that there are two different types of humans: male and female. Nikos tries to intervene when Steg starts to examine Mari a little two closely for his liking. Steg replies by throwing Nikos across the room. While Mari goes to attend to him, Kurt explains that Nikos and Mari are sexually pair bonded, which is why Nikos attacked the commander. Steg then asks if Kurt and Lisa are sexually pair bonded, to which they deny it. Steg loses interest and returns to his task, telling them to stay here and cause no trouble.

After Steg has left, Lisa asks Kurt if he believed Steg. Kurt knows that once Steg is finished here, he’ll kill them all.

The Sontaran guarding the air lock door is attacked by the Rutan disguised as a Sontaran trooper. The Rutan attempts to recharge itself by draining the trooper’s energy. Lieutenant Vorn arrives and interrupts its feeding by shooting it. The Rutan changes back into its original form and flees. After making sure the trooper is well enough to continue its post, Vorn goes to inform the commander.

Steg is studying holographic schematics of the Tiger Moth when Vorn makes his report. Because Vorn hit the Rutan with a full blast, it will have to get more power. Steg orders that troopers be sent back into the engine room and take it apart if they have too. Vorn points out that if they do that the ship will be unable to go. Steg informs his second in command that this ship isn’t going anywhere. Not any more.

The Rutan evades the Sontarans searching for it in the engine room. Vorn and the troopers find the body of the trooper killed earlier.

Kurt is trying to convince Lisa to fight back against the Sontarans. He knows that once the troopers are done here, they’ll blow up the ship simply to keep them from complaining. When she asks about the other ships, Kurt replies, “Same problem, same solution”. Kurt fills her in on everything he learned about Sontarans on Metebelis 3 from somebody called either the Physician or Dentist. Before he can tell her what their weakness is, Vorn enters and takes her away.

Zorelle threatens to tell Steg about Kurt’s plan if he tries to resist. Nikos thinks that fighting back is a good idea, but Mari doesn’t. Zorelle points out what happened to Nikos when he tried. She then tells Kurt not to risk her life to save his.

Vorn takes Lisa to the engine room where Steg explains that the Rutan has interfered with the power unit. Robar’s partially dissected corpse is found in the power drive unit. Steg convinces Lisa that he is not responsible for the engineer’s death and that they have a common enemy. Before she agrees to help Steg seek out and kill the Rutan, she wants his personal word of honour that he will leave her, her ship and her crew in peace once the Rutan is dead. Vorn offers to dispose of the bodies in space, and doesn’t understand why Lisa wants to return Robar home. Sontarans respect death itself and how they die, what is left behind is not important. Steg has Vorn do what Lisa asks. Lisa then leaves to discuss Steg’s terms with the rest of the crew, but not before warning Steg that if he betrays her, she will kill him.

As soon as Lisa is out of earshot, Vorn asks if Steg intends to keep is word. Steg regrets that Lisa must die (“She has the spirit of a Sontaran”). Promises made to inferior species have no validity. A Sontaran’s honour lies in doing his duty. As soon as the Rutan has been found and killed, the humans must die.

Lisa finishes telling the remaining crewmembers about the Rutan and Steg’s offer. Kurt doesn’t trust the Sontarans. Zorelle, trying to curry favour with the commander, tells Steg that Lisa and Kurt are plotting to kill him. Kurt takes full responsibility for the plot. Steg decides to give him the chance. The commander gives Kurt is blaster and dares him to kill him. He might even be able to kill Vorn, then he’ll have two blasters and a group of leaderless troopers. Steg tries to bait Kurt. Kurt suspects something and doesn’t shoot. Nikos takes the gun and tries to shoot Steg but the gun wasn’t primed. This was a test to see who the most dangerous prisoner was – and eliminate him. Steg takes the blaster away from the rash young man and kills him. Mari goes berserk and hysterically attacks the commander. Kurt restrains her while Lisa sedates her. Steg wants to get on with the hunt. They’ll have to hurry as they are now operating with reduced numbers. Lisa angrily points out it was Steg who reduced them.

The Rutan, low on power, possesses the body of the dead trooper in power room and tries to relieve the trooper on guard. The trooper realizes too late that this is the dead trooper killed earlier. The Rutan kills the guard then abandons the Sontaran body to enter the power unit to re-energize.

Commander Steg briefs the crew on the Rutan’s strength and tactics, while Kurt tends to an unconscious Mari. Zorelle is horrified at the idea of a shape-shifting killer able to disguise itself as anyone. Steg promises they will know the Rutan when they see it – it will kill them. The plan will be for the humans to draw the Rutan out and lead it to the engine room or air lock where Steg’s troopers will ambush it. (Kurt: “Oh, great. Live bait!”) Vorn reports that two dead troopers have been found in the power room. The Rutan is now at full strength. Finding it and destroying it will be more difficult that before. Mari is left behind while everybody else goes on the hunt.

The Rutan needs two things: power and escape. Steg goes to join the trooper at the air lock, while Vorn goes to the power room. The humans go to search their designated areas. Soon as the Sontarans are out of earshot, Lisa vows to deal with Zorelle if they survive this. Kurt tells her to leave. They have more pressing problems.

Back in the crew room, the Rutan takes the form of Nikos and kills a sleeping Mari by taking possession of her body.

Meanwhile, the surviving crewmembers have reached the junction where they are supposed to split up. Zorelle loses her nerve and goes back to the crew room to look after Mari. Kurt asks Lisa if they split up. Lisa reveals that she buys Steg’s plan as much as he does. They aren’t going to hunt Rutan – they’re going to help it.

Steg and a trooper take up their positions at the air lock, while Vorn and another trooper take theirs at the power room.

Lisa and Kurt sneak into the power room through one of the service hatches. Lisa sabotages the power drive while Kurt keeps an eye on the Sontarans. They then go to the ‘front door’.

Zorelle, now hopelessly intoxicated, is determined to die with style. Mari appears at the door, but Zorelle is too drunk to notice the girls slightly decaying appearance. When fashion designer asks what she’s doing out of bed, ‘Mari’ replies that someone is in the bed. Zorelle goes to check and finds Nikos’ body. The Rutan then kills Zorelle.

Vorn thinks the power drive is malfunctioning. Lisa convinces him that the Rutan must be inside. Vorn orders the trooper to push Lisa inside, and while the Rutan is killing her, they will destroy it. But Lisa pushes the trooper into the power drive first. The trooper dies horribly. Before a furious Vorn can shoot Lisa, Kurt kills Vorn by shoving a screwdriver into his probic vent. It was something the Dentist told him.

None of Steg’s patrols are reporting in. A frustrated Steg returns to the ship.

On their way to the air lock, Lisa and Kurt come across a wounded Robar. Robar begs for help, but Kurt isn’t fooled. Lisa shoots and the Rutan reverts to its natural form, then disappears. The Rutan made the mistake of calling her ‘my dear’, something Robar never did. Now the Rutan has made this very personal. Kurt gently prods her to continue with their original plan and continue to the air lock.

Steg collects a destructor bomb from the weapons store and takes it back to the Tiger Moth. Lisa and Kurt arrive just as Steg prepares to leave with his surviving trooper. Steg orders his trooper to kill them. The trooper fires but Kurt and Lisa duck out of the way. Kurt fires back, killing the trooper. Steg concedes defeat and prepares to leave; believing the humans won’t kill an unarmed opponent. (Kurt: “Don’t count on it.”) Steg pulls out a hidden gun and shoots Kurt in the shoulder. Lisa shoots Steg, fatally wounding him. The commander admits he should have killed her first and salutes her as a worthy enemy and apparently dies.

The Rutan appears in the form of Zorelle. It shows no remorse for the death of Lisa’s crew putting them down as casualties of war. It vows to go in the Sontarans ship to save its people with the secrets it learned. Then the Rutan changes back into its true form. Steg suddenly snaps awake and tells Lisa about the bomb in the air lock tunnel. Lisa races into the tunnel, primes the bomb and tosses it inside the ship. Lisa races a closing air lock door. Steg holds the door open long enough for her to escape before it opens into space. With is dying breath, Steg crows, “I win Rutan.”

Lisa and Kurt watch from the flight deck as the ship pulls away, then explodes.