Killjoy is summoned once more through a blood pact and wastes no time using the spilled blood of his summoner to forge three underlings—Punchy, Freakshow and Batty Boop. The scene ends abruptly when the man who called him forth refuses to name a victim, leaving Killjoy and his cohort to vanish back to their own world, biding their time.
In a quieter stretch of life, a college student named Sandie watches over her professor’s house while he’s away, joined by her friends Rojer, Erica and Zilla. When Rojer discovers a sack left on the professor’s doorstep, Sandie resists opening it, but curiosity wins out after the others return. That night they uncover an ornate mirror and mount it on the professor’s wall. As the group contemplates the strange find, Zilla dares to examine the glass alone, and he is pulled into Killjoy’s realm, where a menacing boxing match is staged between Zilla and Punchy. The bout is brutal and nearly fatal, but Sandie and the others find his physical body in their world, revive him, and rescue his consciousness from the clown’s dimension. A barrier then materializes around the house, sealing the students inside and severing their link to the outside world.
Erica becomes the next victim of the mirror’s pull, and Killjoy makes his presence felt by speaking to the trio through the glass, inviting them to join him for a grisly feast. He lays out his plan to dine on Erica, and the professor—who summoned Killjoy earlier in the story—returns home to face the unfolding nightmare. He is not surprised by the events, since he himself set these events in motion. The group, drawn through the mirror, enters Killjoy’s world and each member confronts a different demon.
Zilla manages to persuade Punchy not to become Killjoy’s slave, while the professor escapes Freakshow and Rojer is seduced by Batty Boop. Sandie, however, keeps Killjoy’s attention long enough for Batty Boop to confront him with jealousy. The clown’s taunt leads to an intervention that turns deadly for Batty Boop, as Killjoy destroys her. The dinner scene ends in tragedy as the group fails to save Erica, who is torn apart on a gleaming silver platter.
A final showdown unfolds when the professor attempts to neutralize Killjoy by reciting the name Killjoy originally bore in antiquity. He reveals himself to be the father of Michael, whose soul Killjoy had exploited before destroying him. The professor’s gambit is revealed as a cruel plan to use both himself and his students as vectors for vengeance against Killjoy. Killjoy boasts that the souls he consumes become part of him, and the spirit of Michael appears to comfort his father. With the professor momentarily unguarded, Killjoy kills him with the giant mallet, sealing his doom.
Sandie and Zilla, now the last two survivors, try to laugh their way through the terror to drown out the clown, but Zilla is slain when Killjoy taunts them with a cruel humor. Sandie, however, answers with a determined laugh and shouts Killjoy’s original name, a move that incapacitates him long enough for her to retreat back through the mirror to her world. Killjoy explodes in a gory burst of innards as the magic mirror disappears from the wall. Back in the real world, Sandie is shown to be committed for insanity, still laughing uncontrollably and now suspected of murdering her friends and the professor.
