Piranha

“A hideous death lurked unseen in the river...”

Paul Grogan (Bradford Dillman) is a worn-out local drifter, hired by Maggie McKeown (Heather Menzies) to search for two missing hikers, and his hunt leads to a drained pool and the lab beside it. Joe Dante sets the story in a summer resort, with a river upstream and guests in the water downstream. The danger is simple and hard to see, and the people in charge would rather not look at it.