A young woman, who is a dowser, is hired to find water on a ranch with her psychic abilities. Instead, she leads the owners to a buried chest that dates back from the late 1500's. A slow-witted ranch hand is compelled to open it--and when he does we see that it contains a severed head that's still alive. This is the head of Gideon Drew, a devil worshipper. The head soon controls a few people and they locate his body, which is buried in a big casket. However, his plans are thwarted when the young woman takes out a cross and holds it before him. He cringes and retreats back into his coffin. They open it and it's just a skeleton.
This is one of those movies that you think, as a viewer, "What the f*ck were the producers thinking" when they were making this film? Granted, the disembodied head aspect is a little creepy, but the dialogue and turn of events is out of an Ed Wood movie...