An outer space mission goes disastrously wrong as the solo astronaut returning to Earth has a malfunction on reentry. Curiously, the plummeting ship lands fairly intact, horizontally in a cornfield, and the astronaut's body is relatively intact (and is indeed still alive).
It turns out that the reason he's still alive is that an alien has commandeered his body to act as a surrogate mother, and has impregnated him with numerous shrimp-like alien babies.
The other problem is that the alien apparently hitched a ride with him, and is trying to prevent the humans from calling for help until the big plan comes to fruition. It's up to this team, isolated from the outside world, to save the day and thwart the impending alien investigation.
Night of the Blood Beast contains the following tropes:
- Artistic License Biology: While "dead", Johnny manages to have a normal blood pressure. Blood pressure is caused the beating of the heart, and is measured by the highest and lowest pressures in each beat. Since his heart wasn't beating at the time, that's quite the trick.
- Face Full of Alien Wing-Wong: The alien apparently needs other species to impregnate with its shrimp babies. Oddly compared to how this trope is usually played, the victim doesn't seem to mind it and spends the rest of movie trying to convince everyone else that the alien isn't a bad guy.
- Heel Realization: Once the alien reveals its idea of coexistence with the human race, John is appalled to have been singing the alien's praises and gives his life to destroy it.
- Heroic Sacrifice / Redemption Equals Death: spoilered above.
- Mars Needs Women: The titular beast seems much more interested in the female characters than the rest of the cast. Odd, considering that earlier in the film it impregnated a man...
- Mister Seahorse: John.
- Monster Is a Mommy: More like 'daddy,' John is the 'mommy.'
- Shooting Superman: When the monster breaks into the room, one of the other characters immediately responds by shooting at it repeatedly— which was previously shown to be completely ineffective.
- Walking Shirtless Scene: After the group brings John's body back to the base, he spends the entire middle of the film shirtless. Justified at first, because the others were conducting medical examinations; but even after these are finished it is several scenes later before he puts on any clothing.