The commissioner of the Solar Police assembles a group of alien scientists, to assist on a case. Dinagren, a master of disguise, has successfully completed several robberies. The Solar Police are no closer to catching him, let alone identifying him. Professor Ardrey demonstrates his latest invention, a device that records the residual electrical impulses of brain waves. Ardrey records the fading brain wave patterns, at the scene of Dinagren's latest crime.
A police line up of suspects is assembled. Ardrey's machine identifies a rocket pilot, Harlow Prentice, as Dinagren. Prentice protests his innocence, but is, nonetheless, hauled away to jail. Prentice escapes, and confronts Ardrey. Prentice finds Ardrey being held at gunpoint, by Ardrey. Prentice grapples with the gun-wielding Ardrey, who is revealed to be Dinagren. Having stolen enough money to retire on, Dinagren impersonated Ardrey, to frame Prentice for his crimes. Prentice is cleared, and Dinagren is sent to prison for the rest of his life.