A spaceship is sent to Mars after an alien distress signal is picked up. They find one survivor, but when a crew member is found drained of blood it's evident they have rescued a bloodsucking monster. (Uses footage from Encounter in Space (1963).)
| Actor | Role |
|---|---|
 Florence MarlyAlien Queen | Alien Queen |
 Basil RathboneDr. Farraday | Dr. Farraday |
 John SaxonAllan Brenner | Allan Brenner |
 Judi MeredithLaura James | Laura James |
 Dennis HopperPaul Grant | Paul Grant |
| RRobert BoonAnders Brockman | Anders Brockman |
| DDon EitnerTony Barrata | Tony Barrata |
 Virgil FryeControl Panel | Control Panel |
 Forrest J. AckermanFarraday's Aide | Farraday's Aide |
| GGary CrutcherSpaceship Crew Member | Spaceship Crew Member |