One of the first films to feature explicitly gory effects, director Arthur Crabtree's sci-fi chiller begins with a spate of mysterious deaths at an American military base in Canada. Sent to investigate, Air Force Maj. Jeff Cummings (Marshall Thompson) discovers that the experiments of a mad professor (Kynaston Reeves) to materialize mortal thoughts have unleashed a swarm of invisible creatures … who like to feast on human brains and spinal fluid.