Counterblast

In this 1948 film, an escaped Nazi POW named Dr. Bruckner, the Beast of Ravensbruck (played by Mervyn Johns), sets up a lab in England under the name of a scientist that he brutally murders, Dr. Forrester. The Nazi underground wants him to work on a plan to vaccinate the German people against the deadly germs that they plan to unleash on the Allies in the next war.
Bruckner plan is complicated by an inquisitive lab assistant, and further complicated by the later arrival of a beautiful young woman who was hired by the real doctor to assist in the lab. The complications become extreme when the two lab assistant fall in love.
Bruckner develops a deadly infection and an antidote, and he plans to inoculate the female assistant with the antidote, then infect her a few days later. But after his test proves successful, his orders are to kill her and destroy the evidence, but he has fallen in love with her, too. What's a love-struck killer Nazi to do?
The most interesting thing in the film is watching Mervyn Johns. We've all seen him in another movie, the classic 1951 Alastair Sim of version Scrooge. Johns played Scrooge's meek long-suffering assistant Bob Crachit. That film is so ingrained in my mind that watching Johns expertly play a cagey and sadistic killer is a real revalation and a treat. In one scene, Bruckner as Forrester is asked to report to the nearby POW camp because a Nazi prisoner has been injured in a fight. As he treats the prisoner, the injured man denounces Hitler and Nazism. Left alone with his patient, Bruckner without hesitation or remorse dispatches the man with an injection of drugs. The smile on his face as checks the dead man for a pulse is horrifying.