Inspired by real events, The Black Mass is set over a 24-hour period in Florida during the winter of 1978 when college girls were being stalked by serial killer Ted Bundy.

An ex-Navy seal (Mehcad Brooks), his girlfriend (Serinda Swan) and their friends head out on a road trip to New Orleans. The group decides to stop at a roadside convenience store owned by Chopper (Sid Haig), who tells them the tale of Lockjaw, a fabled god-like creature who is half-man, half-alligator.