Set in the wild forests of the Northwest, this film starts off like a serious horror film. Geroge Kennedy brings a real emotional gravity to the film as the father whose daughter is kidnapped by a giant ape in the film's truly scary first scene.
He comes back intending to find and kill the ape but runs into a group of teens out thrill-seeking for Bigfoot, including the well-meaning hero and heroine. Suddenly, two gorgeous girls (one is Michelle Bauer) show up, strip and sunbathe topless. They too are attacked by the ape. Now pay attention. People start turning into zombies and heading for a giant cave in a mountainside. Here we learn that the apes are not really apes but humans who are controlled by aliens trying to get enough slave labor to fix their spacecraft; and as a very sexy perverse thrill, these aliens are stripping beautiful young women and doing Aztec-type cut-out-your-heart human sacrifices. Our heroine is very prettily being prepared for the next ritual, and the hero must find some way into the cave, past the weird slave/zombie/apes. and into the spacecraft to rescue her.
The film is strange and twisted and quite entertaining.