The Doctor has lost Peri in a rainstorm when he's confronted by a being who makes it stop raining. Or actually stops the rain. The being was created, and only a few moments ago, to expect the Doctor.
She works for The Grace, guesstimated by the Doctor to be pan-dimensional beings of immense power beyond scope and understanding. She's on a quest to collect the Keys of Time seeing as he's collected them once before.
After sussing her out and giving her the name Amy, she and the Doctor end up on Mars. The Ice Warriors were at peace, but the Doctor's appearance disturbs things. And while the universe is dying, the leader of the Ice Warriors, Isskar must pass his judgement.
- Accidentally Broke the MacGuffin: The Doctor accidentally did this last time he assembled the Keys of Time.
- Apocalypse How: Mars is heading for a Class X (Causing an X-2). The entire universe is heading for a Class X-4.
- Bigger on the Inside: Amy's purse contains another universe.
- Bizarre Alien Senses: Amy's "tickly" nose can spot the Keys of Time, predict Earthquakes (Or, well, Marsquakes) and could sense soldiers.
- Call-Back:
- The Doctor mentions having been to Mars in a NASA mission not too long ago. Isskar mentions having seen the Ice Lord of that story, Izdaal, commit his Heroic Sacrifice.
- The Doctor mentions he really needs to make a new Sonic Screwdriver.
- The Doctor mentions that he used to know a Zoe.
- The Doctor recalls Nyssa's first taste of chocolate (though that story was released after this one).
- Clarke's Third Law: The Valdigian think everything technological is some form of magic.
- Create Your Own Villain: The Doctor may or may not have caused the Martians to manifest as we know them nowadays, the Ice Warriors.
- Deadpan Snarker: When the Doctor thinks the segment is a Pyramid he quips it'll be easy to steal. When Amy mentions it's the capstone, he mentions it's gotten easier.
- Feel No Pain: Cold-Blooded Torture makes Amy go: "...oooh...aaah..it kinda prickles... I mean it hurts, that's what you want to hear, right?"
- Free-Sample Plot Coupon: The "compass" the Doctor found is actually the first of the Keys of Time.
- Last-Name Basis: Harmonious 14 Zink is referred to as just Zink.
- Long List: The Doctor wishes to name the being made by the Grace, starts with the first alphabetical girl name there is, and keeps going until they hit Amy.
- Hidden Depths: Zink actually has quite a bit of geographical knowledge despite being a money grubbing thief.
- Insectoid Aliens: The Valdigian are described as "More peaceful of the Insect like aliens". 1 minute in the Doctor and Amy are Mistaken for Spies and are about to be tortured.
- Noodle Incident: The Doctor mentions once having been captured in a jelloid prson.The Doctor: It wasn't very pleasant.
- Playing Both Sides: Zara is considered somewhat of a Messiah / Spirit Guardian for the Valdigian, and then sics the Ice Warriors on them.
- Put on a Bus: Peri is lost at the beginning of the episode, and the Doctor wanders off. It helps time itself was frozen, and well, the Doctor has a Timemachine.
- Rewarded as a Traitor Deserves: Zink surrenders after the Doctor him and Amy escape, and as soon as he tells Isskar where the Doctor's headed he gets unceremoniously blasted.
- Sequel Series: The Doctor once again is collecting the Keys of Time. If you count the prose books, this is the second time the Fifth Doctor has done this. Damn thing won't stay collected.
- Single-Biome Planet: The audio starts out on a planet where it's always raining.
- The Slow Path: The Doctor and Amy leave Mars at the end of part 2, and end up in the future (several millennia according to the Doctor) and several lightyears away from Mars. And yet, they manage to run into Isskar. Who's been actively hunting them.
- Sssssnake Talk: Well it featuresssss the Issssse Warriorsssss.
- Time Stands Still: The Grace impose this onto the Doctor in the opening of the story.
- Villainous Rescue: The Doctor gets whisked away at the end, just before he crashes into a star.
- Villain Teleportation: Zara is able to appear as soon as the Doctor states he knows where the segment to the Key of Time is.
- You Have Outlived Your Usefulness: Zara leaves Harmonious 14 Zink behind on a dying planet when she thinks she's "Outgrown him".
- Amy: Wait, what did you do? That wasn't difficult at all! You had me worried!
The Doctor: It wasn't me! I didn't even have a chance to do anything!
Amy: So, then who saves us?
The Doctor: Uhm. I think he did.
Amy: No! But they were not supposed to get involved!
Black Guardian: Doctor! I hope you can explain!
