There are many pubs in London that claim to be haunted. Victorian ghosts, lingering by the stairs, have a way of drawing visitors. One recent evening, the horror director Oren Peli stopped by one such boozer, in an alleyway off the Strand, looked around amiably, and ordered a Coke. He wore shorts, a baseball cap, a paisley shirt, and blue Hokas, and was undisturbed by rumors of a grisly spectral presence. “I’m not a believer in that kind of stuff, but it makes for a cool story,” he said.In 2005, Peli was working as a video-game programmer in San Diego, a job that he hated. He was living in a creaky wooden house, with his “kind of jumpy” girlfriend at the time. “In San Diego, it gets very hot during the day and very cold at night, so the wood expands and contracts,” he said. “The houses kind of groan.” His girlfriend claimed to hear voices and footsteps. “I didn’t hear any of that,” Peli said. But one night, at 3 a.m., they woke up to a loud bang and a crash, “coming from inside the house, for sure, a hundred per cent.” All the doors and windows were closed. “I was, like, ‘What’s going on here?’ ”It turned out that a Costco-size container of laundry detergent had fallen onto the washing machine and then rolled behind an open door. Mystery solved. But the episode gave Peli an idea. “I just thought, What if we got a video camera?” he said, and recorded “all night to see if there’s something happening. Will we be able to capture any proof of anything supernatural?” He never did it (“too lazy”), but “I thought, How scary would it be to watch footage of yourself sleeping” and catch “a little evidence, the door opening, just something that lets you know there is some invisible entity in the room?” He imagined that it would make a good movie.About a year later, Peli used his creaky house as the set for “Paranormal Activity,” a horror film about a couple who record themselves sleeping to try to identify the weird noises they hear at night. The shoot lasted a week and had a crew of three, including Peli and his girlfriend, and a budget of fifteen thousand dollars. After the movie played at Screamfest, in L.A., DreamWorks acquired it, and eventually it got a wide release. It went on to make close to two hundred million dollars and has spawned seven sequels. “Surreal,” Peli said.Cartoon by Roz ChastThe story of the creepy house, and the creeped-out couple, is now running on both Broadway and the West End. There have been some tweaks. In this version, the couple has moved from Chicago to London for a fresh start—bad things happened in Chicago—and the set features a wide town house with dark corners and William Morris wallpaper. Peli was not involved in the stage adaptation, but he had tickets to see it that night with his wife, Staci. “I hope I’m not going to scream,” he said. “That’ll be really embarrassing.”At the theatre, he and Staci, who now live in New Zealand, reminisced about the San Diego house. Peli and the girlfriend who lived with him had broken up, and Staci visited the house after the film’s release. It “looked exactly the same” as in the film, she said. The first night she slept over, the doorbell rang in the wee hours. (A prankster.) Later, a friend stayed in the guest room and was surprised when the lights suddenly went on. (Peli had forgotten to turn off a timer.) “She stayed up the whole night, just so freaked out,” Staci said.