- HD 1080
- Runtime: 76m.
- Status: Released
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- Languages: en
- Country: United States of America
- Director: Charles Marquis Warren
- Stars: John Howard, Mala Powers, Paul Richards, May Wynn, Gerald Milton
- keywords: amazon rainforest, mad scientist, missing person, underground cavern, man with limp, fungus people, primitive village
- Production_studio: Emirau Productions, Regal Films
- Slogan: They dared enter the Cave of Death to explore the secrets of hell!
- The The Unknown Terror is featured in the top rankings of 1957
- #18 in Top Horror Movies of 1957
A woman leads an expedition into a remote jungle to find her long-lost brother, but instead finds a mad scientist who has created a fungus monster that feeds on the local inhabitants.