Probably the second most terrifying thing after someone getting violently angry at you is someone not emoting at you at all. That’s what was terrifying about HAL in 2001: A Space Odyssey. Save for a single red light and some very slight modulation of his voice, HAL was softly spoken and completely inscrutable — expressing himself with the same level of politeness regardless of whether he was helpfully updating David Bowman on the status of the trip or conspiring to kill him.

That incredibly chilling performance will serve as a massive part of Douglas Rain‘s legacy, after he passed away at the age of 90. According to the Stratford Festival, a repertory theatre festival focusing on Shakespeare that Rain co-founded in 1952, Rain died of natural causes on Sunday at St Mary’s Memorial Hospital outside StratfordOntario.

Outside of voicing HAL in 2001 and its sequel 2010, Rain was primarily a stage actor. In 1972, Rain was nominated for a Tony Award for Best Supporting or Featured Actor (Dramatic) for his role in Vivat! Vivat Regina!.