An amateur filmmaker as a teenager, Harrington made several experimental shorts in 8- and 16-mm from the early '40s to the mid '50s, including The Fall of the House of Usher, Picnic, and The Wormwood Star. He also acted in Kenneth Anger's classic 1954 avant-garde short Inauguration of the Pleasure Dome (playing Cesare the somnambulist from The Cabinet of Dr. Caligari). An assistant to producer Jerry Wald in the early '50s, Harrington became an associate producer in 1955 and wrote and directed his first theatrical feature in 1963: the atmospheric fantasy Night Tide, starring Dennis Hopper. Horror has been Harrington's specialty, his films ranging from the low-budget science-fictioner Queen of Blood (aka Planet of Blood, which he also scripted) and the possession terror tale Ruby, to the thrillers Games, What's The Matter with Helen?, and Who Slew Auntie Roo?. Harrington has also worked regularly in television since the '70s, helming horror films such as The Cat Creature and Devil Dog: The Hound of Hell, as well as episodes of Dynasty.