Just when you thought it was safe to go back into the bathroom!

Larry Prentice and his boozy Uncle Ned pull their dilapidated "Satan's Den" Horror on Whells carnival attraction off the highway into a garage for fuel and supplies.

Unbeknownst to them, a priest, hiding in the workshop, is disposing of a squirming bag in a drum of acid whilst denouncing Satan and all who follow him. Suddenly he is set upon by Vicious, oddly shaped creatures who push him into the vat. The Ghoulies are back!

Attracted by the helling images on the Satan's Den truck, they sneak aboard and begin a new reign of terror at the fair!