Bart Hughes (Peter Weller), a mild-mannered, high-flying executive involved in corporate mergers and acquisitions sees his beautiful wife Meg (Shannon Tweed) and young son Peter (Leif Anderson) off on holiday. He stays behind at their costly, luxurious brownstone apartment in New York to work on an important project that could earn him a promotion. While work is stressful enough back home Bart finds himself distracted by a rat lurking in the walls. The increasingly destructive rodent wreaks havoc with the furniture, chews through wires and proves alarmingly resistant to Bart's best efforts to remove it. Eventually, to Bart's horror, he discovers the rat is unusually large, abnormally intelligent and seemingly bent on making his life a living nightmare. With Bart increasingly unhinged things boil down to a savage battle between man and beast.
A decidedly offbeat monster movie, Of Unknown Origin eschews the straightforward killer rodent antics of Willard (1971) and Deadly Eyes (1982) and heads down a more rewarding, ambiguous, darkly satirical route. Adapting the novel written by the grandly-named Chauncey G. Parker III, screenwriter Brian Taggert implies certain allegorical parallels between the man versus rodent battle at the Hughes household and the wider, equally destructive 'rat race' occurring in the world at large in the 1980s. As addressed in the hilarious dinner party scene where Bart gets carried away discussing the effects rats have on the global economy to the disgust of his fellow guests, people are so preoccupied with work and money they fail to notice society is being torn apart. Under immense pressure to score bigger deals, advance to the next rung, earn more money and buy more expensive toys for his fancy home, Bart begins to crack. With impressive skill and subtlety, George Pan Cosmatos charts the hero's slow descent into madness through disorientating sound effects (the growing cacophony of mid-town traffic, the squelch of a knife through a chicken dinner), vivid, scary dream sequences (including a memorable shock moment with future DTV erotic thriller staple Shannon Tweed) and, most notably, a grounded, nuanced turn from future Robocop (1987) Peter Weller. Weller's quirky, endearing performance leaves Bart Hughes far more sympathetic than most yuppie-in-peril characters in Eighties cinema.
Throughout the film, despite icky glimpses of the sweaty, snarling rodent we are never entirely sure whether the malevolent creature is real or the product of Bart's fevered imagination. Aside from a few witty encounters with a wisecracking exterminator (Louis Del Grande), Bart never mentions his rat problem to anyone at the office. Even when Bart's concerned secretary (Jennifer Dale) ventures inside his rat-infested basement Cosmatos maintains an effective, unsettling aura of ambiguity. The lack of any clear-cut explanation for the rat's unusual intelligence and savage grudge against Bart may prove frustrating or ridiculous to some but does not hinder the film from being a compelling suspense piece. Cosmatos creates a palpable sense of unease and otherworldiness with his prowling low-angle rat-cam, teasing use of reflective surfaces and gross-out puppet effects (the odd shot of a real rat proves less effective and too cute), staging at least one common nightmare scenario when the rodent bursts out of a toilet. The film is well paced with sleek photography and an ominous score by Kenneth Wannberg. Still, as a study of paranoia and delusion Of Unknown Origin pulls a few punches concluding on a satisfyingly ambiguous note that it still upbeat enough for the mainstream crowd. One imagines a more nuanced filmmaker like say David Cronenberg would have expanded the psychological dimensions and social satire whereas Cosmatos concentrates on cranking up the suspense and mayhem much like his more widely known action films: e.g. Rambo: First Blood, Part 2 (1985), Escape to Athena (1979), Cobra (1986). He and Weller later re-teamed for the far less substantial underwater monster romp Leviathan (1989).