The Watchmen actor admits no one could understand why a heavy curtain on the set kept moving when there was no one near it and no wind or breeze.

"It was a huge curtain that went from the floor to the ceiling, which was just sort of waving violently and there was no door open or no fan on; no nothing," he tells WENN. "One of the painters goes behind it and couldn't figure out where the movement was coming from. It went on for like, a minute.

"That was a very, very odd occurrence because nothing else was moving around it and nothing else was blowing. You didn't even hear any air, but you watched these curtains sort of violently going. It was pretty trippy. There's a video of it."

Patrick reveals a priest was called in to bless the set before cast and crew started shooting the terrifying film, about two American exorcists sent to help a single mother raising four children alone in a house plagued by malicious spirits, but he insists he wouldn't have been scared if there were spirits with him during the project, because he has a very healthy take on what becomes of lost souls.

"I'm fascinated by people's stories of the paranormal but it doesn't scare me," he explains. "If spirits are out there I don't think that they're bad. I feel sorry for more of them, I guess. That's curious to me."