From Beyond

Dr. Edward Pretorius is a scientist who has developed the Resonator, a machine which allows whoever is within range to see beyond normal perceptible reality. His assistant, Dr. Crawford Tillinghast, activates the machine and soon sees strange creatures in the air. When he is bitten by one of them, he urges Pretorius to turn off the machine. The crazed Pretorius refuses. Crawford panics and flees. When the police arrive, they find Pretorius decapitated. Crawford is subsequently arrested and accused of murder.