It's 1961 and Dr. Paul Armstrong (Larry Blamire) and his lovely wife Betty (Fay Masterson) head into the mountains in search of a recently fallen meteor containing the rare element atmosphereum. Paul needs it to help him with his science work, but Betty'd just as soon have a vacation. Also in the area, sinister Dr. Roger Fleming (Brian Howe) asks trusty Ranger Brad (Dan Conroy) the whereabouts of Cadavra Cave, mysterious home to rumors of a legend of the Lost Skeleton." That night, both parties witness what appears to be yet another meteor falling. Immediately after, a local farmer is killed by a horrible, unseen thing. Is there a connection? Indeed there is. The second meteor is actually a disabled alien spaceship with a strange couple from the planet Marva, Krobar (Andrew Parks) and Lattis (Susan McConnell).

These aliens discover they also need Atmosphereum to power their really high tech ship, and notice their horrible pet mutant (Darrin Reed), which they travel around with for some reason, has escaped. Unfortunately, Dr. Fleming discovers he also needs the atmosphereum to bring to life the dreaded Lost Skeleton of Cadavra which he finds in the cave.

After the aliens disguise themselves as earth people with the aid of their "transmutatron", Dr. Fleming swipes it and morphs four different forest animals into his own ally - the beautiful cat-suited Animala (Jennifer Blaire). Now everyone's after the atmosphereum and the Armstrongs find they have their hands full, capturing the mutant, stopping the evil scientist, and vanquishing the power-mad Skeleton who wants to rule the world.