Garth Marenghi's Darkplace S01 E04 The Apes of Wrath

"FROM THE BEST-SELLING MASTER OF DARKNESS"

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.