Set somewhere after "Gridlock" and before "Utopia".Hey, we haven't had a good Gotta Catch 'Em All serial in a while, have we? Must be time to hunt the wild Plot Coupon.An alien named Baltazar wants to conquer Earth; the Doctor and Martha thwart his plans and send him to the icy prison planet Volag-Noc; he swears vengeance.Some years later. Martha is surprised to run into Baltazar's pet mechanical bird, Caw, whom they had freed when they sent Baltazar packing. Caw remembers Martha, thanks her for his freedom, and gives her a little metal brooch... and a quest.Baltazar, says Caw, has escaped from Volag-Noc and is searching for The Infinite, a legendary old spaceship that grants its finder his or her heart's desire. Caw gives them a datachip, which has the location of the next datachip, etc., all the way to the last datachip, which has the location of The Infinite.First stop: an oil rig on an unpleasant-looking planet. The rig is being robbed by Sky Pirates, whose Captain, Kaliko thinks that the Doctor and Martha are spies from the oil company, and is all ready to make them Walk the Plank when the real spy — her first mate — reveals himself. Bad Guys Do the Dirty Work ensues. The pirate ship is broken up; Kaliko escapes in an escape-pod-thingy, but turns up dead next to the TARDIS. Still wearing her datachip-shaped pendant, fortunately.Next up is the planet of the fish people. Well, planet of the fish person: Mergass, a war consultant; and his clients, a hive of giant alien aphids. Mergass also has datachip-shaped jewelry, so the Doctor and Martha stick close to him while he strategizes with the hive queen about their war against... humans, who also live on the planet. And who, it turns out, were there first, and were attacked by the aphids, and are the good guys for a change. The Doctor brings about peace by posing as a pirate leader, Doctor Vile, of the Mantasphid, in a bit of over-the-top voice work from David Tennant.Last datachip. Why, it's on the icy prison planet of Volag-Noc! What are the odds? The Doctor forgot his get-out-of-jail-free card, though, and finds that the galactic statute of limitations hasn't quite run out on some of his more notorious doings. His stay will be somewhat longer than planned.... unless, of course, he MacGyvers his way out.Turns out Baltazar had played the Doctor for an Unwitting Pawn. He takes the final datachip, takes Martha hostage, and takes off for The Infinite. The Doctor catches up with them—though he later says it's been three years in his timeline—just in time to save Martha from the illusion of her heart's desire (a hologram of himself), but not able to save Baltazar from his (a hologram of piles o' treasure).This was initially shown in serialised form as a regular feature in the BBC's children's Bonus Material show Totally Doctor Who, and later broadcast as an omnibus. Can be watched here
- Arson, Murder, and Jaywalking: The Doctor is incarcerated on over a thousand offenses, including planetary destruction and overdue library fines. He really should've returned those books.
- Continuity Nod: When talking about the Dark Times the Doctor mentions the Racnoss, the Nestene and the Great Vampires. The creature that once inhabited the Infinite is referred to as a Great Old One. In a deleted scene he refers to Fenric, Kwundaar, and Raag, Nah and Rok.
- Derelict Graveyard: The Infinite
- Fantastic Racism: The Mantasphid Queen towards "fleshy bipeds".
- Fish People: Mergass.
- Informed Ability: The Doctor calls Baltazar "the greatest despot who ever, ever lived." Despite the fact that he seems to have no dominion over anything aside from his pirate ship and ends up getting defeated by (in order) a spoon and a robot parrot. Ten likes to exaggerate, though.
- However we do hear that he has just defeated the entire Earth Defence Force and when first seen he comes close to wiping out all life on Earth.
- Knight Templar: The prison governor.
- List of Transgressions: The fake prison governor delivers a list of the Doctor's known crimes to Martha.Governor: Minor traffic violations: 1400 counts. Evading library fine: 250 counts.
Martha: Come on, that's nothing serious.
Governor: Planetary demolition...
Martha: How many counts?
Governor: Seventeen... no, Eighteen.
- Meaningful Name: The robot Prison Governor is called Locke.
- Mysterious Benefactor: Someone keeps helping the Doctor and Martha off screen...
- Out of Time, Out of Mind: The Doctor, when he catches up with Martha and Baltazar, says it's been three years for him, but he doesn't act any different.
- Pokémon Speak: Caw and his son Squawk.
- Pragmatic Villainy: When Baltazar escapes imprisonment, he doesn't seek Revenge, but rather has the Doctor find an object of immense value for him.
- Running Gag: The Doctor still thinks that, no, no, she shouldn't do that.
- Space Is an Ocean: There are pirates and references to the Seven Galaxies.
- The Slow Path: Though it's only been 3 years for the Doctor.
- Whole Plot Reference: This is an animated rehash of "The Keys of Marinus". It also seems quite similar to "The Key to Time", which in the second part had the Captain, a Space Pirate similar to Baltazar.