The cooler water in darkplace is contaminated (and is also bright green)one by one its turns the staff into apes.(with really bad prostetics)
Dag only avoids this fate by a series of contrivances which conviently prevent him drinking his water.
After being attacked he wakes up in the bosses office several weeks later .He discovers the hospital is run by nazi apes and resolves to find the source of the infection.
In a store room they find the source.An ape pissing in to the cooler water containers.
They give chase on bmx bikes and eventually run him to ground. Alls well that ends wells Another aburd classic
i will leave you with the best line of the entire series.
Not my fault monkey bastard hands