When David Garth returned from America, where his speeches on behalf of the Ministry of Propaganda had caused no small amount of concern, he was surprised to receive an unsigned invitation to an address in Wimbledon. He was even more surprised when he was approached by two agents of Department Z. 

Agents Mark and Mike Errol request the assistance of Mr Garth on a mission that has already taken the life of one of their friends. Desperate for vengeance, the Errols are out to catch the cold-blooded killer, ‘Frankenstein’.

After finding his flat burgled with a body lying on the floor, Garth is determined to help the agents clear his own name. But this manhunt unearths a plot with international ramifications: to halt America’s assistance in the second World War.

No Darker Crime is the 20th book in the Department Z series, and was originally published in 1943.