The Eleventh Doctor and Amy Pond arrive on a barren asteroid with a breathable atmosphere and find a large spooky looking house (complete with Gargoyles), high on a plateau. Exploring the run-down house, with remnants of the word "Arkatron" inscribed above the door, the house appears to be empty and abandoned. Inside they find the walls lined with picture frames that, on detecting, play a series of videos that features military generals giving speeches, overlooking battles or some sort of ceremonial occasion but all without sound. The Doctor becomes distracted when he discovers loose wires and finds that defences to the house seem to have been disabled and judging by the footprints in the dust – recently! After more exploring and a scare for Amy, they meet two others in the house – Miss Crisp and Professor Landale. Having recently arrived themselves, Crisp and Landale claim salvage rights to the house and it was them that disabled the house defences.
The early notion that the house was a museum or gallery is dismissed when the Doctor points out that everything is off the same period. When one of the suits of armour is reactivated and attacks Amy, the Doctor uses his sonic screwdriver to deactivate it and discovers a hidden room that the suit was guarding. Inside the room they find an empty bed in the middle of the room with a rolling screen of names at the foot listing the names with the screen headed with the words 'Lest you forget'. More suits of armour stand around the room and from the shadows creeps an unremarkable looking man who demands to know who the newcomers are. The man introduces himself as Lester Forge, the Curator of the Museum of the Ninth Dynasty of Arkatron – a bloodthirsty regime during the time of the dictators. While Crisp has a look around the body of an elderly woman falls from a cupboard and slumps to the floor. Lester recognises the body and says it was his assistant Miss Dellman. As Lester asks what's going on, the Doctor turns to Amy and says he knows exactly what's been going on and is surprised Amy hasn't picked up on the clues....
... The Doctor pieces together the library (full of court reports and records of the atrocities and a trial), the videos (a record of the Ninth Dynasty of Arkatron), and most significantly, in all the backgrounds the figure of a bald little man with glasses shown in some of the videos being led away in chains through the house that would be his prison – Lester Forge! (a name taken in a hurry from the words above the names of the dead). Suddenly pulling out a weapon, Lester reveals himself as the war criminal Maxim Klart – the real power behind disappearances and killings. Trapped in a stasis bed for years and forced to watch the names of his victims, when Crisp deactivated the house's security she unwittingly released Klart who turned on his warden Miss Dellman and killed her. Armed, Klart demands access to a spacecraft that he can finally escape and take more lives. Believing the Doctors sonic screwdriver to be a means of unlocking his spaceship, the Doctor instead uses it to repair the house's security system and once back online, the suits of armour are reanimated and over-power Klart, forcing him back into stasis on the bed. With Klart once more imprisoned, the suits of armour return to their positions and Crisp, Landale, Amy and the Doctor together deciding that the most respectful thing to do is to walk away and leave the place as they found it.
- The Doctor knows the reputation of the Ninth Dynasty of Arkatron and its bloody history under dictators who were responsible for the death of tens of thousands of innocent people. The Doctor hints that Arkatron wasn't always that way but it was during it's rule by dictators.
- Presented in two parts over 8 pages, this was a Whodunit with the reveal being saved in the second half over two pages.