Josh Hartnett, an actor whose heartthrob looks have been detailed in just about every piece written about him, makes quite the unsightly entrance in Showtime’s Victorian-set drama “Penny Dreadful.” Not as one of the classic horror figures at the center of the forthcoming monster mash, but something equally jarring: a Wild West re-enactor donning an extravagantly hairy fake mustache (over a real one) and a flocculent curly wig.

“I just want to be taken seriously outside of my looks,” the 35-year-old quipped, referring to the pause-worthy scene. “But really, it was an interesting thing. The show is so much about what people have hidden, and so for my character to be introduced on stage, in such an extravagant costume, made it all the more stirring.”

Seventeen years after making his breakthrough in the short-lived ABC crime drama “Cracker,” Hartnett is returning to his television roots in “Penny Dreadful.” Set to bow May 11, the tale of monsters and men tinkers with the origin stories of a number of leading figures from gothic literature (e.g. Dracula, Dorian Gray and Frankenstein). Hartnett plays Ethan Chandler, a sharp-shooting American actor who takes on the role of a hired gunman in London.

After coveting an under-the-radar existence by appearing in a string of indie films — no doubt contributing to Google’s suggested search phrase “What happened to Josh Hartnett” when his name is entered — “Penny Dreadful” aims to put that question to rest. Hartnett is alive and well. In fact, he’s been here all along, even while you weren’t looking.

“Penny Dreadful” is poised to be a looker. A departure from Showtime’s roster of pill-popping nurses and mentally ill CIA agents, the dark psychological thriller with an eight-episode first season has an enviable roster of talent behind the camera: playwright and screenwriter John Logan (“Red,” “Skyfall”) is the driving force, Oscar winner Sam Mendes is among its executive producers, and Juan Antonio Bayona (“The Orphanage”) directs.

Hartnett wasn’t lured by the intricate world concocted so much as he was seduced by Logan’s pitch. In particular, “collaboration” and “partnership” caught his attention at their initial meeting.

“It was important to find an actor who you would believe was a man of action — a man who could use firearms and hold his own in a fight — but more importantly find an actor who behind their eyes had a certain amount of suffering,” Logan said. “And a certain amount of lived-in intensity. That is Josh.”

Hartnett is among an ever-expanding list of film actors jumping onto the television bandwagon. The transition hasn’t been without its challenges.

“I kept asking John where the character was coming from,” he said, catching himself on more than one occasion referring to the series as a film. “I needed to know. He was like, ‘I don’t know yet. You kind of have to leave your options open or just choose something.’ It was something I couldn’t wrap my brain around. What if I choose the wrong thing? It’s been a learning experience.”

In other ways, it’s been a surreal experience, he added. Hartnett said the cast of horror characters roaming the Dublin, Ireland, set made for plenty of unusual sights.

“The poor guy who plays a vampire, his name is Robert (Nairne), I just feel so bad for him,” Hartnett said. “It’s not warm in Dublin in the wintertime, and they try to keep heaters around whenever possible, and there is poor Robert — super skinny and super tall, in a girly silk robe in full vampire makeup and teeth just shaking because all his paint will come off his body if he isn’t careful. I don’t know if I could handle a gig like that.”

Hartnett’s Ethan Chandler is enlisted by a seductive clairvoyant (Eva Green) to aid an African explorer, played by James Bond alum Timothy Dalton, who lost his daughter to the city’s malevolent creatures. But just don’t call him the star.

“They’ve been advertising my face on the billboard, which is surprising,” Hartnett said. “Really in the first few episodes, you won’t see me that much … and that’s OK. Ethan is a slow burn. I like that.”