Someone's carelessly dumped a shitload of angel dust into the water supply of a 'city somewhere in Northern Europe' (Frankfurt must have objected to itself being name dropped). The first indication of this is rats coming up out of the sewers to eat fornicating couples in cars but what we've really tuned in for is the animals at the local zoo who've drunk contaminated water and are going ape.
Way more 'Italian' in approach than similar animal attack films like 'The Beasts Are On The Streets' watch if you want to see rats being burnt to death in slow motion with a flamethrower, an elephant standing on a woman's head, the frightening power of a Polar Bear on Angel Dust, a cheetah racing a Volkswagen Beetle and pre-teens killing adults.
Utterly bonkers in terms of blasé animal handling and reprehensible in terms of animal treatment ... films like this just couldn't be made nowadays.