Garth Marenghi's Darkplace - Season 1 Episode 4 The Apes of Wrath FROM THE BEST-SELLING MASTER OF DARKNESS
Overview: Monkey business most macabre. A terrible sickness is spreading from ward to ward as humans regress to a primal state. Dr. Rick Dagless M.D. must kill the beast within us, and fast. i.e. before it's too late.