Sapphire and Steel reveal to the Harboroughs that they think they will be the next victims, as they are the youngest. Steel wonders how humans destroy each other, and Sapphire, with greater understanding of humans, comments that they have so many ways.
Annabelle Harborough is the next apparent victim, but Sapphire and Steel tell Harborough that in reality nobody has been murdered, it is because for consistency's sake everybody not alive in 1930 is having to be eliminated.
Naturally Harborough does not accept that their explanation, so Sapphire locks him in the room from them, and they tell him who they really are. They show him the truth by showing him the people who have apparently died, talking to him. They focus on Greville the butler, who has just found that the door handles that killed Harborough's wife were electrified. Of course all this is merely to keep him busy so that Sapphire and Steel can focus on the real mystery. This is an inversion of the distraction motif in this assignment: so far 'it' has been attempting to distract Sapphire and Steel, but now Sapphire and Steel are distracting the humans to keep them occupied.
Sapphire manages to drag the office back to the present, and Steel uses parts from the radio to generate a signal that will open the door. I like this bit for the total lack of social grace with which Steel pushes the secretary out of the way to use her computer. As he returns to the drawing room the door returns to its 1930 appearance.
It is also apparent in this episode how Sapphire and Steel actually complement each other very well, as she plays bridge with the other guests, and charms the secretary into helping them. Meanwhile Steel is operating the computer remotely by waving his finger around. She won't help them, but of course Steel has got the answer. George McDee's body was found in the ashes of the library, according to the newspaper report they find.
Sapphire and Steel use Harborough as a spy to find out the details of McDee's work from Lord Mulreen. They enter the office - transformed back into the 1930-era laboratory. Harborough picks up a culture which McDee knocks into his face. Harborough interrupts Sapphire and Steel's argument about whether there could ever have been a fire in the library by entering the library and dying, with a burned face. The library clock strikes midnight - it is the day when the world will end, June 22nd, 1930.
This episode changes the feel again, to a more normal Sapphire and Steel episode, where they begin to act to deal with the time disturbance. The Christie novel fades into the background to allow this to happen.