In a solar system far, far away (namely, the ex-Thanos System), there's a planet where time has fragmented. A corporation, as corporations do, has decided to try to make a profit off of this. They've taken the various time zones of the planet and sold them to a variety of buyers. Some use the time zones as penal colonies, some as old age homes, and others as toxic waste dumps. Meanwhile, a station on the moon controls all these times zones, keeping them from destabilizing and ripping the planet apart.
Unfortunately, the station on the moon is itself falling apart. The Doctor and Sam stumble upon it as one of the members of the three-person crew has gone missing, one has gone mad, and one is being attacked. If that weren't bad enough, a mysterious ship is approaching the station.
Then everything really goes crazy. The madman on board the station transmats Sam down to the surface of the planet right into the middle of a revolt going on at one of the penal colonies, the time zones on the planet begin to destabilize, and a warlike army arrives trying to gain knowledge of time that they can use to conquer the galaxy. The Doctor races against time, literally, in order to save Sam, the planet, and the rest of the galaxy.
Tropes present in Longest Day include:
- Conqueror from the Future: What the Kusk want to become, using the knowledge from their probe
- Ground Hog Day Loop: One of the many time distortions on Hirath
- Ripple-Effect-Proof Memory: Anstaar assumes that the people stuck in time loops don't have this, but the Doctor says he's not so sure...
- Temporal Sickness: An effect of the time distortions on Hirath
- Time Crash: The crashed time probe was causing this on Hirath.
- Time Travel for Fun and Profit: The corporation controlling Hirath doesn't have a time machine, but they're certainly making a lot of money off of the distortions caused by someone else's.
