The episode begins with Sarah Jane getting kicked out of the nanotech factory she's investigating, and returning home. Cue alien-related emergency. This time it's a Captain Tybo the Judoon hunting an escaped prisoner. Androvax, Destroyer of Worlds, is a Veil: a species whose hat is Grand Theft Me. Surprise, surprise, he possesses Sarah Jane, and Luke, Rani and Clyde have to track her down while keeping Cowboy Cop Tybo from doing too much damage. Androvax orders Mr. Smith to self-destruct, but Luke talks him out of it. Rani's folks visit the nanotech factory to promote Gita's flower business and get arrested.
Androvax heads for the nanotech factory and releases the nanoforms to build him a spaceship and destroy the Earth. Captain Tybo's Judoon buddies arrive, confronting, scanning, and scaring the crap out of the newly-escaped Chandras. Rani and Clyde lock up Tybo, who is soon freed by the Judoon. Everyone has a nice little reunion in Androvax's new space ship, where Luke uses the controls to deactivate the nanoforms. Androvax gets arrested, Clyde and Rani get grounded, and everyone goes home.
- Blatant Lies: Nothing to see. Move along. Said by a space rhino escorting a green reptilian prisoner.
- Also, Androvax-as-Sarah Jane is not very good at pretending to be Sarah Jane to Mr. Smith. He only "get away" with it because he threatens to destroy Mr. Smith's CPU if he keeps asking questions
- Body Snatcher: Androvax
- By-the-Book Cop: Captain Tybo, who obeys the speed limit and pays and displays.
- Cowboy Cop: Tybo again.
- Chewing the Scenery: The possessed Sarah Jane.
- Doesn't Like Guns: Sarah Jane's reason for investigating rather than leaving things to the professionals is that both UNIT and the Judoon carry guns, "and that spells trouble."
- Evil Is Hammy: Androvax, especially in Sarah Jane's body.
- Grey Goo: The nanoforms
- Heroic Willpower: Subverted, then played straight by Sarah Jane.
- "I Know You're in There Somewhere" Fight: Subverted when Androvax tricks Luke by using Sarah Jane's normal voice.
- Large Ham: Sarah Jane, while possessed by Androvax.
- Move Along, Nothing to See Here: Tybo to the Chandras at the end.
- Nano Machines: Called nanoforms here.
- Woobie, Destroyer of Worlds: Androvax's backstory makes him this.