‘What an absolute twat!” cries Matthew Rhys, clutching his face in both hands. He has just been reminded of a remark he made in 2000, when he was playing the Dustin Hoffman role in the West End stage version of The Graduate. He was 25, not long out of Rada, and was asked if he could imagine being middle-aged like his Mrs Robinson, Kathleen Turner, who was 45 at the time. His response? “Yes – and it’s frightening. I wonder – will I still be acting?”

Perhaps the “frightening” part merits derision. But acting is a precarious business, so no wonder he questioned his career’s potential longevity. “It is precarious,” he says, grateful for the off-ramp. He is wearing a black T-shirt and speaking over video call from the Brooklyn home he shares with the actor Keri Russell, their 10-year-old son and her two teenage children from a previous marriage. “It was after The Graduate that I had my longest stretch out of work. I thought I’d made it, and then I was like, ‘Nope’.” His prospects were so dire back then that he applied to join the army, only to be rejected by a recruiting officer convinced that he was merely researching a role. “I remember him looking down my CV at the list of acting jobs and saying: ‘I’m very confused …’”

Now 51, the Cardiff-born Rhys is all smiles despite the “Celtic lid” over his eyes which he once said lends him a naturally downcast look. His career is anything but precarious. He has just returned home after six months shooting the second series of the thriller Presumed Innocent. The reason for our conversation today, though, is his lead role in Widow’s Bay, a supremely entertaining horror-comedy that plays like Schitt’s Creek or Northern Exposure reimagined by Stephen King. Directed by Hiro Murai, best known for Donald Glover’s Atlanta, and created by Katie Dippold, one of the wits behind Melissa McCarthy vehicles such as The Heat and the 2016 Ghostbusters, it succeeds in raising laughs and goosebumps.

Rhys plays Tom Loftis, the mayor of Widow’s Bay, a quaint New England island town where a rumour persists that no one born there can ever leave. Tom, who is originally from the mainland, is trying to bring in the tourists, not scare them away, so naturally he plays down the area’s gruesome folkloric past, and denies reports of ghosts and ghouls running amok on the island.

Widow’s Bay caps an impressive couple of decades in which Rhys has become one of the most compelling figures in US television. He spent five years as Sally Field’s gay lawyer son on Brothers and Sisters, won an Emmy for playing a Soviet spy undercover in the US in The Americans – which was where he met Russell, who starred as his screen wife and fellow KGB agent – and was nominated on four other occasions, most notably for his guest spot as a toxic celebrity novelist, the very personification of #MeToo, in the American Bitch episode of Lena Dunham’s HBO hit Girls. He also stepped up when Robert Downey Jr was unavailable to play the title role in the gritty 2020 reboot of Perry Mason. And he was alternately charming and chilling as a property developer and suspected killer opposite Claire Danes in last year’s Netflix thriller The Beast in Me.

A streak of mordant humour runs through even his darkest characters – witness the scene in The Beast in Me in which he horrifies Danes by boogying brazenly to Talking Heads’ Psycho Killer. But Widow’s Bay gives Rhys a rare chance to play all-out comedy. One highlight is Tom’s dinner with a New York Times journalist who he hopes will write a puff piece about the island. Up until that point, Tom has been walking on eggshells, a frantic, Basil Fawlty-esque mania surfacing as he tries to put on a good show for his sophisticated guest. But when the journalist reveals over dinner that he adores Widow’s Bay and can’t understand why it doesn’t already have the profile of Martha’s Vineyard, Tom briefly loses control. He yelps excitedly, then clamps a hand over his mouth as if trying to shove the unseemly noise back in.

“I remember thinking: ‘Let’s just try it,’” Rhys says. “It was a big-swing moment. The whole thing is a big-swing project for me. It’s out of my comfort zone – it’s a bit ‘death or glory’ at times – but I loved every second of it.” In another way, though, it continues his pattern of playing outsiders, which served him so well in The Americans. It also pertains to his own life, as a Welshman who has now been living in the US for 20 years.

“The parallels were not lost on me,” he says. “Not to get too ‘armchair psychologist’ about it, but it connects also to growing up. As revered as culture and the arts are in Wales, there weren’t many of us doing it. At my very sporty school, I’d be, like: ‘Oh, I’m the only bloke in drama club.’ I was an outsider even then.” Was he hassled or bullied for that? “Not massively. My mates would take the piss a bit. It was banter.” That, he says, is one of the things he misses most about the UK. “The level of sledging you get is Olympic standard. Sometimes when Keri comes back with me, she says: ‘They’re so mean to you!’ In Britain, the great equaliser or denominator is how well you take the piss out of someone – and how well you can take it yourself.”

Rhys was an outsider, then, long before he left the UK. “And now I come to a different country and I’m definitely the outsider here. Weirdly, that never goes away. Even though I live here, New York is still, for me, Robert De Niro in Mean Streets. And you’re always reminded of your differences. Gabriel Byrne used to say: ‘You carry it like a hump on your back.’ It’s not quite a hump for me but it’s an awareness that you never shake. That was the great parallel for me with Tom. The same with The Americans – a foreigner pretending to be an American. I was like: ‘God, I’ve founded my career on that!’”

He has come to dominate TV. But what about movies? His Hollywood resumé is not too shabby: Steven Spielberg directed him in the journalism drama The Post, with Tom Hanks and Meryl Streep, and he teamed up with Hanks again as a troubled reporter interviewing the wholesome entertainer Mr Rogers in A Beautiful Day in the Neighbourhood. Then again, he also fluffed a James Bond audition in the early 2000s by joking to the producers that he would consider playing the spy with an eyepatch or a limp. How far does he crave a film career now that his TV one is in such rude health?

“I don’t any more,” he says. “I think TV is the perfect medium for me. I’ve made movies with huge stars, so I’ve checked that box. But I like the slow burn of episodic television, the luxury of being able to take your time.”

He certainly doesn’t want for complex roles. Tom in Widow’s Bay may initially be a comedic presence but he has his demons, too. That special duality in Rhys has been apparent since at least as far back as The Scapegoat, a 2012 Daphne du Maurier adaptation on ITV in which he played doppelgangers.

Even he was taken aback, though, to be offered The Beast in Me. “I was like: ‘Are you sure this is for me?’ I thought they’d sent it to the wrong guy. What did they see in me?” It’s likely the producers spotted him in Girls, I suggest: his character cruelly but skilfully manipulates Hannah (Lena Dunham), who has written a blog criticising him for using his power to prey on young women. Lulling her into a false sense of security with a mix of intellectualising and flattery, he then plops his penis out of his fly. No, Rhys didn’t get to keep that silicone semi. “I did ask,” he says glumly. “I wonder what they did with it. I hope it got disinfected.”

He maintains that age has a lot to do with the more textured parts he is offered now. “As you get older, you can tap into your emotions far more easily. You’ve lived a life so there’s more to draw from.” What would he see today if he looked at his films from the late 1990s and early 2000s? “I didn’t have much acting experience then, so it was all a bit vanilla. A bit shit. It comes for free with the years, the interesting stuff. And thank God for that.” Middle age, then. Not so frightening after all.

Widow’s Bay is on Apple TV from 29 April.