AllMovie

After playing on a strange-looking harp, Dr. Smith (Jonathan Harris) ends up where everybody said he would end up...or so it seems. Transported to what looks like Hell, Smith comes faces to face with the demonic Morbus (Gerald Mohr), who demands the destruction of the aforementioned harp, else Smith will remain "down below." It takes the combined efforts of Don (Mark Goddard) and Judy (Marta Kristen) to rescue Smith and prove that Morbus isn't exactly whom he claims to be.