The G-32's cargo bay is almost full. In the distance are the mountains of the planet Vinsk. The human crew are loading the G-32 under the supervision of armed guards. Lorraina watches her co-worker, Magnus, open a crate and berates him for stealing from the Zalnex Corporation. He takes out a bottle of hand wash called Gemini that claims to kill viruses and teach languages. Lorraina is not interested. He asks her if she would like to speak Vinskan so that she could understand the locals. She asks why, when they already speak English

The TARDIS travels on. Amy has just woken up and peers into the control room. The Doctor is darting round the console. He tells her they are going to arrive in 2112 at the anti-viral handwash factory where Gemini is made.

Magnus squirts some Gemini onto his hand. The Mexican, Ramirez, arrives near them. Magnus offers him some of the hand wash. In seconds both men are clutching their heads. Their veins stand out on their face. Lorraina screams so loud she doesn't hear the TARDIS arrive. Both men shout at her, "Listen to me".

The doors open in the TARDIS and Amy asks the Doctor if the Time Lords had their own language. As they step out they see Lorraina backing away from two convulsing men. As they close in on the girl, Amy runs along the gantry to intervene. Ramirez stomps towards her. The Doctor steps in and shines a light from his screwdriver into the Mexican's eyes. He stops in his track. Magnus grabs at her while she tells the Doctor that the men used the hand wash. Lorraina dodges away from Magnus and falls through a gap in the gantry. She plunges several levels. Magnus and Ramirez disappear through a door. Amy suggests that they return to the TARDIS but the Doctor picks up the bottle of Gemini and sniffs it.

Heavy boots approach. The Doctor tells her it is time to return to the TARDIS. As they go towards it a group of security men approach. The Doctor hides her behind some boxes and then presses a button that lowers her section of the gantry one level. Before he is arrested, he whispers down to her to hide.

The Doctor is held at gunpoint by two guards, Turner and Moran, while an American - Hank Musselbrook - interrogates him angrily. He grows annoyed at the Doctor's failure to give his name and punches him unconscious. Amy sees the Doctor dragged off to Zalnex Tower. She is shocked to see the huge doors of the cargo bay clang closed. She also sees the TARDIS carried away on the back of a vehicle.

When the Doctor wakes up he is in a room with the three guards. It is a corporate office which also contains a seventy-something year old man. The Doctor reads the man's name as Denton Vale, the Zalnex CEO. He uses a failed attempt to shake Vale's hand as an excuse to stroll around the office. The Doctor is shocked to learn that Amy and the TARDIS were not in the factory as he intended but in the cargo hold of a ship.

The Doctor denies that he killed Lorraina but blames the handwash for mutating the two co-workers, thus causing her to die. He says that

The handwash is a noble idea but something is wrong with it. He says he needs to meet the creators of Gemini.

Amy walks through the corridors, realising that she is on board a ship that is about to launch. She sees Ramirez lying in a storage room. A security guard levels his pulse rifle at her, telling her he has kill clearance. She steps towards him and reads his name badge, Swanson. He tells her she is under arrest but just then Magnus bursts out of a room and grabs the guard, shouting "Listen to me!" Ramirez does the same to Amy. She asks him to let go and wants to know what he is trying to say. Swanson looks at his hand, covered in the handwash, and joins in the chant of "Listen to me". She presses a button that shuts a door on Ramirez and allows her to slip away from him.

The Doctor is escorted through corridors to a large laboratory. Scientists are hard at work in the sunlit room. A tall, slender alien approaches. Vale introduces his chief scientist, Corn Paloa. She is aloof and graceful. Her eyes are large and oval, her face framed with white fur. She is accompanied by Jim, a rotund human. The Doctor notes that nobody wants to shake his hand. He asks her what the active ingredient of Gemini is. Paloa tells her that it is Meme-Spawn. This saddens the Doctor and puzzles Vale, who has evidently never heard of them. The Doctor explains that they are sentient micro-organisms that drift through the galaxy absorbing language. He is indignant that they have been put into handwash but Paloa says she only used cloned spawn. This does not mollify the Doctor. Vale is astonished that live creatures are in Gemini but the scientist insists that she told him. She is evasive when the Doctor forces her to admit that it has never been tested on humans. She protests that Vinskans are essentially similar to humans and they were the test subjects. Vale says that a product recall is impossible. Jim takes a bottle of Gemini from the scientist and rubs the handwash into his palm. Almost immediately he is grating the words "Listen to me." The Doctor says that this is what the cargo bay workers were saying. The Doctor orders the other scientists to evacuate as Jim launches himself at Paloa. The Doctor and the guards step in but Jim fights them off. He smears Gemini on the guard's hands and Turner and Moran are transformed too. The Doctor tells Musselbrook not to shoot as he, the guard and scientist race out of the door even as Vale closes it.

Captain Clive Taylor is looking forward to launching and returning to Earth. His co-pilot, Velma Henshaw, points at a monitor. He is astonished to see a scene showing Amy attacking a set of instruments in a corridor with a golf club. He sees several guards approach her but neither he nor Henshaw, beside him, see that they are stumbling erratically. Amy is trying to prevent the ship being launched. Henshaw wonders if she is an ethical protestor. Meanwhile, Amy is trapped between two men. She swings her club at a door button. A door opens but two more shrieking, black-eyed guards approach.

The Doctor watches Jim raging in the laboratory. Through the sound-proof glass the Doctor offers a reassuring smile, resolving to try to bring the men back to themselves. The Doctor tells the people around them that the men are trying to speak every language in the universe at once. Vale wonders why they are speaking English. The Doctor realises that it is the telepathic power of the TARDIS, routed through the Doctor and Amy that is translating the words. He decides to ignore the question. Instead he says that the Meme-Spawn gives them an insatiable urge to communicate. As he watches, Jim's mouth opens wide. The Doctor decides that the virus is mutating.

Amy also sees the four guards sit down and open their mouths. Something like a slimy green starfish with sharp teeth propels itself from one of the men and hits the wall. Three more are ejected from the other men.

The Doctor and his companions see three starfish hit the observation window. The Doctor tells them to close the vents in the laboratory but one of the starfish escapes through a vent and hits one of the security guards. It bites him and he begins to transform. The Doctor realises that he has to stop the G-32. He drags Paloa into a lift. Outside he hears pulse-fire and shouting. A starfish leaps through the closing door and bites both the Doctor and Paloa but he tells her that, as non-humans, they are immune.

The wind blows cold over the roof of the Zalnex tower. The roof's launch pad is lined with sleek passenger cruisers. The Doctor shows his psychic paper to two guards. It indicates that he is Vale's son. He puts the paper away and then takes it back out. This time it seems to be a pilot's licence. The Doctor and Paloa barely make it into one of the cruisers before Musselbrook arrives to stop them. Paloa points the way and the Doctor takes off for the G-32. Rifle fire sounds from below as they depart. Paloa voices her fear that the Gemini virus will infect the whole of the Zalnex tower. As they cross the sky they are shot at from behind by another cruiser containing Vale and Musselbrook. The Doctor dodges the laser bolts until a direct hit cuts a hole in the hull. Musselbrook aims at the fuel tank. Suddenly a mutant starfish leaps from behind the seat. The security man pulps it with his fist but not before it has bitten him. He intones, "Listen to me" and grabs Vale.

Looking in his mirror the Doctor watches the chasing cruiser nosedive into the ground. They carry on their way, just in time to see the G-32 launch into the sky.

Amy finds Taylor and Henshaw unconscious outside the flight deck. She steps past them and notes that the instrument panels have been smashed. As the two pilots awake, snarling "Listen to me" she closes the door on them. The pilots push at the door. She sees that the autopilot is on. Just then the Doctor calls her on the intercom. The Doctor pilots his cruiser up to a shuttle bay door and tells Amy to open it for her. She tells him that Zalnex have taken the TARDIS away. After a moment of silence she starts to repeat "Listen to me" over and over. He tells her to open the doors for him and, surprisingly, she does.

He pilots the cruiser into the bay and lands it safely. The door closes automatically and they head for the flight deck. The G-32 enters outer space. They run along empty corridors to a deserted flight deck. There is no way of changing the destination coordinates. Paloa flicks through the security monitor and states she has found the crew.

They arrive at a window to the cargo bay where all of the infected are gathered. Some are unconscious and others are shouting to be heard. Amy is among them. The Doctor tells her to force the virus from her mind. Amy is dimly aware of the disturbance but returns to her task of explaining the universe to a room full of deaf ears. The Doctor uses the sonic to see that the doors are all locked in a multiplicity of ways. Even pulse rifles have no effect. The Doctor tells Paloa that the humans will die soon due to the physical effort. Paloa is appalled and asks him to do something to save the others. The Doctor ponders the self-destruct system and then dismisses it. She says that if she had known what the results would be she would have burnt her laboratory. Suddenly the Doctor recalls that the Meme-Spawn need the air to be cold to thrive: too warm and they will die. This is why they have gathered in the hold, which is always the coldest part of the ship.

Amy recovers consciousness with no memory of how she got into the hold. The air is hot and heavy. The others are waking, too.

Later, with the cargo ship back in the Vinsk atmosphere, the Doctor and Amy hear Paloa on the intercom. She says that she is on the flight deck and there are only three minutes until the ship self-destructs. She wants to be certain that all of the spawn are dead. She tells him not to try to rescue her. He takes the cruiser, with all of the crew aboard, and leaves the ship a long way behind. As they put the miles between them and the ship, the G-32 blossoms into orange flame.

They arrive at Zalnex Tower as night falls. The Doctor asks if anyone knows where the factories are and where the air conditioning is. Ramirez tells him that the factories are in the tower and the air-conditioning is on the top floor. He fires energy bolts from the cruiser's weapons at the top floor. He calls down to watching officials that they can evacuate the tower in a few minutes. He tells Amy that the building is full of generators and will start to overheat within minutes, killing the spawn-clones.