Dr. Bruckner, a Nazi scientist infamously known as the Butcher of Ravensbruck, kills Dr. Forrester, a British bio-chemist, and assumes the dead man's identity. The murder is part of a post-war plot by fugitive Nazis to perform germ warfare experiments in England. Bruckner is determined to develop a strain of plague virus to use in a future war against the victorious Allied forces. His initial experiments with animals are promising but he needs a human subject to proceed further. He convinces his unsuspecting young lab assistant to be his guinea pig, injecting her with the deadly virus followed by the antidote. If she survives the treatment, his work will be completed, but he'll be forced to kill her to cover his tracks.
Counterblast is a post-war thriller from England that brings a bounty of Hitchcockian suspense elements to the screen. The evil Dr. Bruckner is played by Mervyn Johns, and his fiercely menacing portrayal is in stark contrast to his most famous role, filmed three years later - that of Bob Cratchit in the 1951 film version of Dickens' A Christmas Carol, with Alistair Sim.