Adam,the 46 year-old vampire in a sixteen year old's body returns to school,where his attempts at banter referencing 1980s pop culture fall flat.he does befriend Christa,whom he recognizes as a werewolf though she is in denial. Only they can see Matt,the tubby ghost of a boy who went missing.Adam knowing that he was murdered and his killer be exposed before he can pass on. Chief suspect is school bully Danny whom Matt terrorises with his psychic powers but admits it was only for revenge because he is sure the boy is innocent. Brandy Mulligan,self-assured and glamorous...
The trio pursue Brandy but Matt remembers that he was killed in the boys' toilets and he is sure she was not there. Then they learn that sadistic sports master Swan wants the toilets completely cleaned and painted but before they can gather evidence Christa becomes a werewolf,sniffing out the location of Matt's corpse. They find themselves facing the killer and the door appears for Matt to pass through. But will he go now that he has found his new friends?
In the school laboratory Adam and Christa see a tubby boy called Matt, for whom there are Missing posters. Only they can see him so he is plainly a ghost. he believes he was murdered but cannot remember who did it. As Christa and Adam ponder aloud teacher Mr Roe suggests they try Brandy Mulligan, a girl whose family has criminal connections.
Brandy Mulligan seems a likely suspect as Matt has recall of being in a girls' changing room so Christa and Adam pursue Brandy, pointing out that they know she is a member of the notorious Crompton family. Brandy is hostile but Matt suddenly recalls that he saw her leave the changing room so that she cannot have killed him.
Matt remembers school bully Danny holding his head in the toilet but again cannot recall if this was his last memory. Adam and Christa are concerned that they might be wrongly seen as a couple but are interrupted when they see Mr Roe argue with another teacher Mr Swan, whom Roe accuses of being a bully himself. Christa tumbles to the fact that CCTV in the boys' toilet might give them a positive answer about Danny.
CCTV footage leads Adam and Christa to the gym, where they hide in the vaulting horse as Swan comes in and vigorously attacks a punch-bag. He is aware of their presence but when he discovers them they pretend to be passionately kissing. Matt, who fancies Christa, gets the wrong idea and has to be told they are acting in his interests. A full moon is due soon and werewolf Christa feels this may be to their advantage.
The trio become certain that Matt was killed in the gym and Christa, transforming into a werewolf, is convinced that her heightened sense of smell will lead her to the body and thence to the murderer. For his own safety Adam has to lock her in a cupboard but next morning after she has changed back they make a discovery.
The trio discover Matt's body in the cupboards containing the gym equipment but they are interrupted by the actual killer, who explains their motive for murdering Matt. There is a fight, during which the killer passes through the door intended for Matt, who now considers staying around with his two new chums.