A nerdy young kid named Michael likes a girl named Jada, but she is seeing a gang member named Lorenzo. Michael is asking Jada out at the beginning of the movie, to the disgust of Jada's friend Monique, but Lorenzo and two of his thugs show up and beat the crap out of Michael. An odd homeless man witnesses all of this.
Michael goes home and uses black magic to call upon the spirit of Killjoy, a clown doll. But one of Lorenzo's guys calls out to him from the street, and gets him to come downstairs so they can talk about Jada's feelings for Michael. Stupidly, Michael listens and is grabbed by Lorenzo and his goons. They take Michael out into the woods, where Lorenzo pulls out a gun and threatens to kill Michael. When his thugs protest, Lorenzo clicks the gun and nothing happens. He just intended to scare Michael, and pulls the trigger again to demonstrate that the gun isn't even loaded. The gun goes off and Michael is killed. Lorenzo and his boys scram.
Fast forward to a year later. Jada is studying with Jamal, who tells her to remember Michael and stop seeing Lorenzo. Jamal and Jada have sex, as Killjoy rises and attacks Lorenzo's two hoods, taking them through an ice cream truck into his own realm. He kills them. We then see Monique and Lorenzo having sex. She asks him where he sees himself in five years, and he gets upset. Killjoy then sucks Lorenzo into his world, where visions of the two thugs appear and tell Lorenzo to kill Killjoy, but Lorenzo himself is killed by multiple bullets to the chest.
Naked Monique wakes up and finds drops of Lorenzo's blood trailing to the ice cream truck, where she finds Lorenzo's body. She screams, and the mysterious homeless man appears.
Monique calls Jada, who heads over to her place with Jamal. The homeless man recaps the plot up to the point, and says Killjoy will be after them next. The only way to kill him is to destroy his heart and also the clown doll. Then the man vanishes.
Jamal, Jade and Monique find the ice cream truck and enter Killjoy's world, where undead Lorenzo and his boys show up to fight them. The good guys kill the bad guys (again), but then Killjoy appears and apparently takes out Monique and Jamal. Jada agrees to kiss Killjoy in exchange for him never appearing on Earth again, but Killjoy lies. Then Killjoy reveals that he is really Michael, and all he ever wanted was for them to be together: Will she be his girlfriend? Jada agrees, but when she hugs Michael, she stabs him in the heart. Michael falls to the ground, and Jada reunites with Jamal and Monique, but Killjoy reappears with Lorenzo and the good guys realize they have to destroy the doll. They gather in a circle at the place where Michael invoked the spirit of Killjoy, and Jada has to stab Michael again in order to send him to Hell, where Killjoy informs Michael that their deal has been broken and destroys him.
Jamal, Monique and Jada return to their world and live happily ever after.