Poirot is issued with a deadly personal challenge when a series of letters, mysteriously signed ABC, lead him to a string of brutal murders where Poirot could be the next victim.
Old wounds are reopened when Lynley investigates the disturbing death of his godson, more than a decade after the boy's disappearance.
When all the children in the world suddenly stop in their tracks and in unison chant the phrase 'We are coming', the Torchwood team know they have an alien force to reckon with, but how is the government involved?
Torchwood are forced into hiding underground to avoid the government squad's action against them and their families. Meanwhile, the government makes plans for the mysterious Floor 13.
The eyes of the world turn to Britain, as the 456 announce 'We are here'. Meanwhile, Torchwood are forced to set up a new temporary base, and must break the law in order to get the things they need.