Killjoy is back in the fourth installment of the demonic clown series. This time Killjoy is being accused of not being evil, since he let one of his victims(Sandie) get away. Killjoy must rely on his only chance of proving how evil he really is... get Sandie into hell as his witness.

After their human test subjects turn into animalistic horrors, a small group of scientists barricade themselves in their laboratory, but they must balance moral conflict with survival as their botched creations attack.