OK, I like a killer rat movie as much as the next cat. And I don't know what I was expecting from OF UNKNOWN ORIGIN but it wasn't this! Very pleasantly surprised. Peter Weller plays a yuppie (it WAS 1983) who is bucking for a promotion by over-achieving on a super-important case at work. His wife and kid are off to the grandparents' house so this should be a golden opportunity for him to ace it. Except for the apparently golden retriever-sized rat that chooses Peter Weller to mess with!
The film is a great snapshot of obsession as the anal-retentive Weller character slowly slides from chastising his son for knocking the hall rug askew to bashing every square inch of his home to smithereens. The rat (who is a she, by the way) goes from playing playful-ish pranks on Weller to fiery-eyed vengeance when, at one point, Weller dumps her newly-born baby rats down a basement drain. For Weller and the rat . . . it's now personal!!! The uber-rat is obsessed with gaining vengeance on the murderer of her babies while Weller's character is obsessed with eliminating this destructive intruder. At one point, a beautifully-telling piece of dialogue occurs when Weller's assistant shows up outside and Weller shouts down from an upper window for her to "just leave them alone". The only relationship Weller is now concerned about is between him and the rat!
Here is a movie that really is like a rollercoaster ride in that the first two-thirds find us cranking, cranking, cranking methodically up to the top. Once the peak of the rollercoaster is reached, the final third of the film careens wildly down into unhinged mayhem! Rat and man are at each others' throats. What a great, fun thrill-ride!