"...and Shakma! Shocking audiences everywhere! SHAKMAAAAAAARGHH!"
Sam and his girlfriend Tracy both work as lab technicians at a highrise office building housing a medical research facility, for scientist Professor Sorenson. In particular, it's Sam's job to look after the animals used in Sorenson's work, and he has a particular fondness for a baboon named Shakma.
Along with Sorenson and their co-workers Gary and Bradley, they enjoy playing a LARP
called Nemesis in the building after hours, and one night they schedule a game after all the other employees have knocked off for the night, inviting their friend Kim to play with them. Unfortunately for them, Sorenson had earlier performed some questionable brain surgery on Shakma, in an apparent attempt to reduce his aggression. It didn't go well, and the experiment apparently got reversed - Shakma instead became dangerously aggressive and started attacking people.
Sorenson orders the baboon destroyed, but Sam injects him with the wrong chemical and simply sedates him. Then thanks to further bad luck, Sorenson's assistant Richard forgets to process the "dead" animal in the facility's incinerator, instead leaving him lying unrestrained on a table. As the five friends and their surprisingly cool boss begin their LARPing adventure, none of them are aware that the sedative is beginning to wear off, and Shakma is starting to awaken...
- Absent-Minded Professor: Sorenson.
- And Starring: Roddy McDowall is billed this way in both the trailer and the opening credits.
- Animal Testing: Probably not the best idea to take an already aggressive animal like a baboon and screw around with its brain.
- Antagonist Title
- Casting Gag: Hmmmm, Roddy McDowall in a film where mutated apes hunt and kill humans. Where have I heard that before?.
- Bland-Name Product: The game, which is called Nemesis.
- Closed Circle: The gamers are trapped inside the medical building.
- Note that this is by design - Sorenson locked certain rooms to limit where the players of the LARP can go.
- Despair Event Horizon: Sam crosses it when Tracy dies. Then he crosses it again after the death of Kim.
- For Science!: No explanation is ever given for why Sorenson's was monkeying around with baboon brains. The creepy narrator in the trailer suggests, "It started as an experiment in human aggression," but the movie itself never gets around to an explanation.
- Headphones Equal Isolation: A variant of this with Laura in her car with the window rolled up and the music turned on really loud.
- Heroic BSOD: Sam while he's laying out the bodies of all his dead friends and co-workers.
- Hollywood Acid: Richard tries to kill Shakma by throwing a beaker of acid at him. Unfortunately, the baboon jumps him and he spills the stuff on himself. We don't see the effects immediately, but half his face is dissolved when Sorenson finds him later.
- Hope Spot: When Kim and Sam notice Laura is sitting in her car outside. Unfortunately, she first ignores them and then misinterprets their efforts to signal her as Richard screwing around, and drives off in a huff.
- Idiot Ball: Gee Tracy, don't you think you could have just articulated to Gary that there was a dangerous lab animal on the loose and people are dead instead of just vaguely sputtering to him in sentence fragments and dramatic pauses not to go to the fifth floor?
- Sam, as well. He avoids telling Kim about Richard's death, despite the fact she is very visibly distressed and worried about him. Needless to say, the second she's left alone, she goes looking for Richard and gets killed by Shakma.
- Kill 'em All: Maybe even Sam dies in the end leaving only Richard's girlfriend Laura alive, who drives off in the middle of the movie.
- LARP: A rare pre-internet era example. The main characters are each assigned a character and the research building is their gaming area.
- Lowered Monster Difficulty: Shakma is all about ripping his prey to shreds for most of the movie, but during the final confrontation he briefly attacks Sam and then runs away.
- This may be due to the fact he was quite affectionate with Sam before the experiment.
- Madness Mantra: "It's all my fault" for Sam. And later, "I win."
- Maniac Monkeys: The titular primate is a genetically altered baboon with a murderous attitude.
- Murder by Cremation: Sam tricks Shakma into leaping into the specimen disposal crematory and torches the baboon.
- Nice Job Breaking It, Hero: Sam, Sam, Sam... First, he injects Shakma with the wrong chemical, sedating him instead of killing him like Sorenson ordered him too. The movie is ambiguous on whether or not Sam did this intentionally. Then, later, he doesn't tell Kim about the death of Richard, which results in her wandering off to find him and gets killed herself.
- Poor Communication Kills: See Idiot Ball entry.
- Pyrrhic Victory: Invoked. In the end, Sam, exhausted by his wounds, lays on the ground and finds it darkly humorous that he "won" the game.