It's hard to imagine Buckaroo Banzai or Robocop losing their mind over a minor pest problem. But in the thriller Of Unknown Origin, Peter Weller plays Businessman Bart, an anal retentive New York exec just ripe for a crazy-making at the hands of a rat in the walls.
The pressure is on at work, so when his wife and kid go away for a week, Bart is free to concentrate on his TPS reports. He has his huge newly renovated brownstone to himself, until a rat chews through his dishwasher hose, starting a cascade of destructive events that inevitably erode the poor man's sanity. Weller as Bart looks like a dark brooding Paul Reiser. His first mistake in dealing with the rat problem is consulting the troglodytic weirdoes that live near him. They add fuel to the fire of his anxiety by detailing the gruesome superpowers of the world's greatest rodent, which he then parrots back at a fancy dinner party, in the movie's most intentionally funny scene.
Pictured: the movie's most unintentionally funny scene. Yes, that's a fake rat bursting out of a kid's birthday cake.
He does himself no favors, relaxing at home with videos of lab rats cannibalizing each other, and beating the ceiling with a copy of Moby Dick. Bart is seen perusing a (real) National Geographic article called "Rat: Lap Dog of the Devil," and looking at gory photographs of human rat bite victims. Allusions to other stories of men doing obsessed battle with animals are frequent; Bart dozes while watching Spencer Tracy in The Old Man and the Sea, and warns a guest against going to the attic: "It's very Edgar Allen Poe up there." He begins to lose a handle on his work, and he can't even concentrate on the affair he's trying to start with his secretary.
"This subtle and efficient weapon should keep rats out of my kid's birthday cake."
The rat, in the meanwhile, gets bigger and smarter and more malevolent. "It" becomes a "she" and develops the motivation of protecting the nest and yes, even revenge. As she becomes more like a human, Bart becomes more like an animal. As Bart completes his transformation into a rat-killing machine, the wreckage that ensues seems ludicrous. However, when you realize that the director went on to make Rambo, it's a miracle that the city block is still standing at the end of the movie.