What happens to the mind when you’re confined to a life of solitude? Robert Eggers offers his interpretation in his latest film, The Lighthouse, a psychological horror shot in haunting black and white.

Set in the late 19th century, it follows elderly lighthouse keeper Thomas Wake (played by Willem Dafoe) and his assistant Ephraim Winslow (Robert Pattinson) as they spend a month tending to a lighthouse on an isolated island.

Things get weird almost as soon as the two men arrive ashore. New recruit Winslow finds a mermaid figurine, inciting visions of a beautiful humanoid creature washed up on the shore, equal parts erotic and disturbing. He sees Wake naked in the lantern tower of the lighthouse and has distressing dreams.

Psychologist Sarita Robinson at the University of Central Lancashire, UK, says that hallucinations are common when people are in isolation, usually occurring if there is also sensory deprivation, such as being in a dark room.

In an experiment conducted at McGill University in the 1950s, volunteers who spent days alone in tiny rooms began to hallucinate after a matter of hours, becoming so distressed that the research was terminated early. “Humans are social creatures – we crave the company of others,” says Robinson. “We know that social isolation is really damaging for both mental and physical health.”

As the film unfurls, it is clear that having only the brash and authoritative Wake for company is taking its toll on Winslow. “It’s bad luck to kill a seabird!” Wake bellows at him over dinner as he slaps him across the head. Winslow is shocked and more than a little peeved.

Soon after, as Winslow’s time on the island nears its end, the wind changes direction. The ferry meant for Winslow never comes and a raging storm breaks out. The two men start to lose their grip on reality with Winslow becoming increasingly infatuated with the lantern tower, which Wake has forbidden him to enter. All the while, they drink themselves into oblivion.

In stressful situations like these, people secrete more oxytocin – a hormone involved in social bonding – which could lead to the development of more friendly relationships for support and protection, says Robinson. Indeed, also spurred by the alcohol, there are glimpses of almost tender moments between the pair, who sink deeper into their fates that now seem intertwined with that of the island.

Pattinson exercises an impressive range of emotion in his portrayal of the fragile Winslow, from fanatic anguish to tortured ecstasy, including a masturbation scene that might possibly be the most intense in cinematic history. Dafoe, meanwhile, plays the more measured, but arguably just as damaged, Wake with ferocity and unpredictability.

Director Eggers creates a world that is both beautiful and unsettling with the stark imagery of crashing waves and looming rocks interspersed with violent flashes of tentacles and blood. The intermittent blast of the lighthouse’s foghorn throughout is just enough to immerse you in the mental anguish plaguing the characters without giving it to you too.