Julian Reed has apparently gone barking mad. He's seeing aliens everywhere, and finally has a public breakdown resulting in confinement to a psychiatric facility. David Vincent comes to investigate, and must decide whether Reed is really mad, or if the Invaders actually have infiltrated Reed's place of employment, the highly secret Slaton Research Center.
When Julian Reed accuses David himself of being an alien, and when Julian's wife Pat seems reluctant to even see her own husband, David doesn't know how to proceed, until a chance encounter between a dog and one of the guards at Slaton reveals that at least one alien has found his way into the organization.
- Joanne Linville as Professor Pat Reed
- Donald Harron as Jeff Brower
- Kent Smith as Edgar Scoville
- Charles Aidman as Prof. Julian Reed
- Simon Scott as Dr. John Slaton
- Johnny Jensen as Frankie Reed
- Bartlett Robinson as Art Llewellan
- Noah Keen as Paul Meyers
- Dort Clark as Security Officer
- Pat O'Hara as Scientist
- Lisabeth Field as Mrs. Fielding
- Michael Harris as Security Guard