The warriors of an African tribe jump into action when a very dangerous cyclops attack their
village. Their skills aren't enough to stop it, so they seek the help of a legendary monster hunter,
who is getting ready to fight. But the origins of this story actually began many years ago: teenage
boy Jack was always in trouble because he was constantly angry and snapping at anyone over the
smallest things to the point of actually getting violent. His teachers would always punish him with
detention or extra exercise and make him apologize to his victims, but nothing was enough to make him
stop. It wasn't always like that, though. Jack used to be a good boy that lived happily with
his family until the fatal day they went camping. His parents had been dancing to music on the radio
and Jack copied them with his sister, but the girl whirled away into the forest. Suddenly,
a troll appeared and began eating the kid, Jack was so scared that he froze and could only watch.
The parents rush to help, but the troll ate the mother too. The father tried to retaliate and the
troll quickly overpowered him, so right before dying, he told Jack to run. After watching his
dad get eaten too, Jack ran as fast as possible and became the only survivor. Nowadays, Jack is
in his twenties and still carries an anger that he unleashes easily. He's working on getting better
though: he's got a job as a plumber, started night classes to finish high school, and sees Counselor
Silverstein for guidance. However any question asked by Silverstein just triggers another
furious rant from Jack and no progress is ever made. Tonight Jack is arriving late at school,
which is pretty usual for him and doesn't surprise Professor Crowley. Jack's girlfriend
Eve does pass him notes to scold him for missing most of the class and not even bringing a pen,
but Jack pays more attention to the other girls in the room. Tonight Crowley shows the students
how sodium can make an explosion when put into water. As soon as the class is over,
Eve rants at Jack for being so irresponsible, and classmate Jone comes to offer his notes to
help but also to flirt with Eve. Jack is starting to get irritated but luckily before he can snap,
Crowley calls him over. The professor also scolds Jack for always arriving late, but most
importantly he asks for his skills as a plumber because he's having trouble with the pipes in his
new house. A few moments later, Jack arrives at Crowley's place and meets his dog Waldo. The house
is still being tidied up, and Crowley explains he got it super cheap because it has some nasty
story behind it. Jack goes to the basement to start working on the pipes, and once he's done,
he asks Crowley to try the sink. Unfortunately the repairs don't work and as the whole installation
breaks down, the valve hits Jack in the face. Meanwhile outside, the ground opens to show
something glowing. Jack explains to Crowley that they need to change the valve, so he takes the old
piece and promises to come back after finding a replacement. At first his van won't start,
and Jack begins throwing a tantrum that is interrupted when the engine finally reacts,
stopping things before they get violent. Sometime later, Crowley falls asleep at his desk. Waldo is
outside barking at the hole in the ground, which now is releasing a mysterious smoke. This smoke
sneaks inside the house through the back door and is inhaled by Crowley, who suddenly wakes up and
abruptly stands up to reveal black eyes. Moving rather awkwardly, Crowly runs through the house
and hits the door with his own body a couple of times until he realizes how to open it, then he
runs to the garden even if it's raining. The next day, Crowley wakes up when he hears Waldo bark at
him. He's shocked to discover he fell asleep in the garden and his hands are rather dirty as if he
had been digging, not remembering a thing about last night. When he turns around, he confirms
digging is exactly what he had been doing. The hole isn't very deep yet, but now Crowley is
curious and rushes to get a shovel to finish what he started. After some more digging, Crowley finds
the broken pipe and a mysterious box, which he proceeds to take out of the hole by chaining it to
his truck. Once the box is taken into his office, Crowley opens it and finds a human skeleton.
He gives a leg bone to Waldo then looks more closely to find a huge surprise: inside the ribs,
there's a black heart still beating. A wary Waldo barks at it but Crowley picks it up anyway and
tries to make it stop moving, however this only gets his fingers covered in goo. Suddenly his
hand moves on its own and pushes the heart into Crowley's mouth, forcing him to swallow it whole
before falling unconscious. Meanwhile Jack goes to the hardware store to get a new valve. The clerk
Howard is shocked to notice the valve is a model he hasn't seen in years, and when Jack says where
he found it, Howard is terrified. He asks the boy to come back tomorrow for the new piece and
promises to share the story about the curse behind that house. Back to Crowley, he wakes up with a
burp on his office floor. He can't stop scratching his chest and feels extremely hungry, so he goes
to check the fridge. He tries the lettuce and spits it out, but ham and milk he adores,
it seems he's ravenous for animal products only. In the evening, Jack arrives at class on time and
the one to arrive late is Crowley, who looks like a complete mess. His clothes are dirty, he keeps
on burping and scratching his chest, and there's still food in his hand. When one of the students
asks if he's sick, he just laughs and says a little. Then Crowley turns to the blackboard
only to start writing nonsense, causing everyone to laugh right before he throws up all over the
board. Crowley tries to clean it with his sleeve and decides to end the class for today. Outside,
Jone tries to flirt with Eve again. When Jack walks by, Jone tells him he has to treat Eve
better and insists Jack needs to relax, not letting him go until they have a talk. Growing
irritated, Jack hits him in the throat, and now he has to drive Eve home while she yells at him
for being violent during the whole trip. Crowley goes home too and arrives with a bucket of fried
chicken because he can't stop eating. Waldo won't come closer to receive his master and barks every
time he sees him. Crowley ignores him and goes looking for more food, only to stop when he
feels a weird sensation in his stomach. A bump on his shirt begins moving on its own and suddenly,
a tentacle comes out of his body. Freaking out, Crowley grabs it with both hands and struggles
against it until he can find a pair of scissors to cut it off. Afterward, Crowley checks the fridge,
but there are only vegetables left. Since Waldo won't stop barking at him, Crowley chases after
him to have him for dinner. The following day, Jack tells Silverstein that he thinks
he should move to another country to start over. Silverstein points out Jack is only trying to run
away from his problems and insists they should talk about Jack's family tragedy. Jack doesn't
want to talk about it because everyone makes fun of him for saying he saw a monster, and he
still feels guilty for running away. Silverstein says that's exactly the source of Jack's anger:
he can't forgive himself. Later, Jack goes to see Howard to get the new valve. Howard freaks out
again and after having a strong drink, he shares the story. When he was a little boy, Howard went
to live in that house with his uncle Emmet. This man worked as a researcher and he traveled the
world collecting things. An item he brought from Japan was a black heart sealed in a glass case,
and little Howard was fascinated by it. The legend said many years ago a demon had crept its way into
our world with the purpose of spreading evil among humans. A group of men destroyed the demon and its
heart was kept as a trophy, but it was said evil still lurked in it. It passed through many hands
and shops until Peter bought it at an antique store. One evening, little Howard was looking
at the heart and accidentally dropped the box, cracking the glass. Later, smoke started to sneak
out of the box and took over Peter's mind, making his eyes go black. Just like Crowley,
Peter began behaving weirdly, feeling constantly hungry and eating enough to feed a small country.
Little Howard was getting scared and checked the box, only to find it empty. Sometime later,
Howard heard noises outside and discovered Emmet eating their dog. When Howard came closer,
Emmet bit the kid and ate his hand. Terrified, Howard managed to pull his arm away and run
into the house, where he search for his uncle's rifle and used it to kill him. Afterward, Howard
put Emmet in a box to bury it in the backyard, and he was sure he could still hear the heart
beating. Jack doesn't understand how a kid could drag Emmet into a box and dig without a hand,
so Howard shows him his hook replacement to prove it. This is still not enough to make Jack care,
and he leaves after paying for the valve. Later at school, Jack tries to apologize to Eve for last
night, but this only triggers an argument that ends with Eve wondering if they should see other
people. Jack doesn't hesitate to accept to break up, causing Eve to get offended by how quickly he
was ready to get rid of her. When they enter the classroom, they find Crowley sleeping on the desk
and his sleeves stained with blood. Two students drop a heavy book on the table and the noise
wakes Crowley up. After belching, Crowley walks around still scratching his chest and looking
disorientated. He also throws up again, and as his stomach gurgles, he loses control of his arm.
A worried student approaches him to check on him, but Crowley pushes her away, hurting her. Then he
turns to reveal there's a giant tumor growing on his chest, not to mention he's spitting blood. The
students run away in fear and Jack makes sure to help the hurt girl walk away as Crowley falls to
his knees. His body begins transforming into an extremely grotesque form and tentacles come out
of his back, which he sends down the corridors to capture the students. Jack, Eve, and the girl hide
in a classroom, and Jack manages to close the door right when a tentacle tries to enter, cutting its
tip. The other students aren't as lucky, and the tentacles drag them back without caring if they
get hit by any object in the process. When the students are brought back into the classroom,
they discover Crowley has become a disgusting beast that has covered the place with goo. The
black heart can be seen beating on his aberrant body. His first victim is Jone, who gets pushed
to the floor before Crowley inserts one of his tentacles into his mouth to fill him with his
toxic fluids. A moment later, Jone stands up to reveal he's a monster too, and Crowley sends him
to find the missing trio while he takes care of the next student. Meanwhile Jack is trying to
use cables to tie the door. Eve keeps freaking out because she thinks they should leave, not
lock themselves up, and Jack grows irritated by her constant screaming and the girls crying over
a small wound. At that moment, Jone bursts into the room. Eve runs away, but the other girl isn't
fast enough and Jone grabs her. Jack tries to save her to no avail and realizes Jone is eating her,
so he runs away too. While Crowley sends out more transformed students, Jone finds Eve in another
classroom. Luckily Jack arrives just in time too and hits Jone with a stool before grabbing
Eve to run away. There's another monster waiting outside, so the couple runs down the corridor only
to find the doors closed. The janitor is on the other side and accepts to open when he sees them,
but he takes his sweet time with it. This gives the monster time to catch up, and by the time
the doors are unlocked, the monster jumps on the janitor to eat him too. Jack and Eve run
to Jack's van, which takes a while to start. Eve yells at him for driving an awful vehicle,
making Jack's irritation grow. To make matters worse, the radio begins playing the same song he
heard when his family died. Jack suddenly stops the van as flashbacks of the tragedy flood his
mind, and Eve yells at him for it. Jack's anger grows and finally makes him snap, but this time
it's different. He asks Eve to get out of his van, furious but without violence, then he drives back
to the school. Jack's determined to make up for the errors of his past and arms himself with all
his plumber tools to stop the monster. In the corridor, Jack finds two transformed students,
fighting over the janitor's body. They both attack him as soon as they see him, and a fierce yet
unfair fight begins. Jack manages to push the boy away for a moment to kill the girl by hitting her
head with his pipe. Then he goes after the boy to punch him repeatedly until he falls on the floor,
where Jack stabs him with a tool. Meanwhile Crowley feels hungry again and begins feeding
on one of the students. Jack begins making his way to find Crowley, but he bumps into Jone first. A
chase begins through the school, and Jack defends himself by throwing anything he can find at Jone.
However Jone feels nothing and comes close enough to bite Jack's arm. Jack headbutts him to push
him away, then he breaks the lab equipment to bludgeon Jone to death. Afterward, Jack wraps
up his wound with tape and takes a fire axe before running into his classroom, where he finds Crowley
making more monsters. Using the axe, Jack cuts the tentacles to allow the students to escape,
but Crowley begins attacking him before he can finish. Jack tries hiding under a table and
throwing his axe at Crowley directly, but nothing works, and now a newly transformed student is
attacking him too. Crowley tosses the axe away and laughs as he watches Jack and the monster fight,
but his laughter dies when he sees Crowley break a cabinet door and use it to kill the
monster. Now the cabinet is open, Jack sees the sodium from last class and remembers his
lesson. He rushes to grab it right before Crowley captures him with a tentacle to drag him closer,
and Jack takes advantage of the new position to insert the sodium in the monster's mouth. Shocked,
Crowley drops Jack as he tries to spit it out, but the sodium explodes and takes his head. However
the heart is still beating and controls the tentacle, capturing Jack again. This time, Jack
manages to retrieve his axe and cuts the tentacle off before running to the monster and attacking
the heart, finally killing him for good. All the tentacles fall off and the remaining students run
away as Jack approaches the final girl to kiss her to celebrate. This adventure has changed something
in Jack, and now he knows monster hunting is his call. First he returns to the forest to kill the
troll that ate his family, finally giving the matter closure. Then he starts traveling the
world fighting monsters, and now he's in Africa, ready to fight the cyclops to save the village.