The evil Dr. Mabuse develops a death ray with which he threatens the world.

A company's stockholders hold their meeting at a lonely mansion. A mad doctor conducting experiments in the mansion starts to strangle them one at a time with a nylon noose. The survivors must figure out a way to stop him.

A British woman on a visit to post-war Berlin is caught up in an espionage ring smuggling secrets into and out of the Eastern Bloc.

Professor Mauthner, after many years of exile (having emigrated in 1933 to the USA), returns to Germany in 1948. He can in fact return to his teaching post, but the rejection and petty intrigues of his reactionary colleagues and students make his work almost unbearable.