Paul and Eddie are veteran paranormal monster hunters and a new recruit named Vanoss desperately tries to join their team. They get alerted by an old lady that her house was taken over by ghosts who are partying to loud music. Paul and Eddie leave Vanoss behind, since he is inexperienced. They, aided by Pad - an extremely intelligent supercomputer designed to detect paranormal activity - and Orb - a football-sized magical sphere containing a powerful and immortal female being inside - , infiltrate the party and realize that the ghosts cannot leave, because they are controlled by DJ, a demon called a Canaanite Lord of the Covenant. The two find out how demon is controlling the ghosts: through the music. As they are cornered by the demon, Vanoss arrives to the rescue and changes the loud techno music to Paul's romantic tape, which destroys the demon and releases the ghosts.

The team are hired by a school principal to take care of a Shapeshifter problem at the school. They manage to drive the Shapeshifter away from the school, but it falls in love with Eddie. After taking many forms to get closer to Eddie - even through Vanoss and Pad -; the Shapeshifter assumes the form of Eddie's deceased wife Jill, who was killed by Sasquatch. They quickly start a relationship based on lust and everything seems to be going fine, until one night, Sasquatch invades Eddie's house, savagely rips the Shapeshifter to pieces and escapes.

Paul is trying to resurrect his childhood puppy shepherd dog Cinder using a device he created. However, things go awry and he unknowingly resurrects a zombie elephant which then proceeds to attack the local circus. Meanwhile, Eddie is training Vanoss in defensive hand-to-hand combat. The group is alerted by Pad about the havoc the zombie elephant is causing and they - minus Vanoss - go to the circus. Paul talks the zombie elephant down from doing any harm, but Eddie arrives and shoots it anyway, causing it to burst open and release a couple dozen mini-zombie elephants who run away. Paul and Eddie try to resurrect Cinder again and they succeed. Zombie Cinder rounds up the mini-zombie elephants and they allow Paul to put them out of their misery. Paul then has to euthanize zombie CInder, which he remorsefully does.

Alerted by Pad; Paul, Eddie and Orb go to a local bar that's getting thorn up by a vampire. A brawl ensues, Paul chickens out and Eddie is bit by the vampire. A rival paranormal activity hunting squad called the Destroyers arrive, led by the narcissistic Dunham. Eddie turns into a vampira and kills a few people, becoming a target for Dunham. Vanoss tries to calm his bloodthirst with his mother's badger, which Eddie promptly sucks dry. They learn that the only way Eddie can revert to his old stae is if they kill the vampire, who is hiding in a nearby cave. En route to the cave, the Destroyers attack vampire Eddie, but Vanoss arrives and incapacitates Dunham. Paul and Eddie enter the vampire's lair; and after being mocked by the vampire for his cowardice at the bar, Paul snaps and uses a nearby sword to decapitate the vampire, reverting Eddie to a human. Dunham arrives and congratulates Paul and tries to coerce him to join the Destroyers, but he and Eddie flip him off.

Eddie and Paul go out to the forest looking for a tree to cut down for Christmas, but are attacked by a snowman possessed by a Muckus Demon, a descendant of the Krampus who wants to destroy Christmas. Eddie quickly kills the snowman, but the demon possesses the tree they take home. Meanwhile, Paul and Eddie activate Paul's gift for Christmas: a more advanced, highly intelligent flying robot named Cy, who is discreetly trying to take over Pad's role. The possessed Christmas tree awakens and feeds off electricity to grow in size and strength, then it heads for the city. Pad feels leaves, and Vanoss tries to join the team. They follow the tree to the power plant, where the tree uses the power to grow. Cy betrays the others and leaves. The others realize that the only way they can stop it from absorbing more power, is by disrupting the electricity, meaning that somebody has to sacrifice himself. Pad returns and jumps into the electricity, overloading the tree with too much power and destroying it, sacrificing itself. However, Orb uses her powers and resurrects her. Pad is willing to forgive them if they beat Cy to death, which they happily do.