Talk all you want about methods and prep and training versus instinct and natural talent, but ultimately acting will always remain a bit of a mystery to most of us. Billy Crudup is a good example of why.

His shape-shifting physicality alone is pretty inexplicable. In a 2002 Broadway revival of The Elephant Man, he conveyed John Merrick’s monstrous deformities without makeup or prosthetics, relying on painful contortions of his body so believably that The New York Times’ Ben Brantley found him virtually unrecognizable. In one of his earliest leads, the 1998 biopic Without Limits, his gait so closely matched that of runner Steve Prefontaine that his scenes could be seamlessly intercut with archival film of the Olympian’s races. And then there was shamefully under-seen Stage Beauty, where he played a man playing a woman considered one of 17^th-century London’s most ravishing actresses, a role Salon said he understood so well in his bones the performance actually read as a woman playing a man playing a woman.

And then there’s the mystery that transcends the physical, one we suspect is deliberate. Crudup’s characters hold something back, never completely knowable. And when you think about it, what’s more believable than a human who keeps at least some part of themselves hidden? More practically, it keeps us riveted. When an actor can go from charming to menacing to smarmy and back again, virtually without changing expression, we never feel quite safe looking away. The New York Times called it “kinky chameleonism,” and Vulture took note of it in a review of Spotlight. “Billy Crudup nearly stops the show as a super-smooth, super-friendly, 100 percent phony lawyer.” (We won’t argue with the show-stopping part, but read on for the real scoop behind the performance.)

All of which makes him an excellent actor, but a hard-to-place leading man. Hollywood needs a “type” to pin such roles on. But for most of his career, Crudup’s been okay with that. His acting experience was largely in theater at the University of North Carolina and then grad school at New York University’s Tisch School of the Arts, but within two years of earning his MFA, he was getting film roles in indies like Sleepers and Inventing the Abbotts while turning down opportunities in more commercial projects like Titanic and Hulk. He inadvertently landed in a classic when Cameron Crowe’s Almost Famous became an unexpected hit, playing rising rock star Russell Hammond. He needed some guitar lessons for the role, but the unforced charisma he brought to it is beyond teachable.

The downside of becoming a golden god is that it can blind folks to even better work in your archive, such as the aforementioned Stage Beauty. And Jesus’ Son, in which he played the drug-ridden, road-tripping FH. New York Magazine was one of many voices praising his work. “The great thing about FH is that though he’s a woozy drifter, his eyes, his face are always shockingly alive. Crudup has a great physicality, and he gives FH’s gangliness a loose-limbed lyricism.“ The performance almost made one major actress refuse to work with him on a subsequent film – she didn’t want someone she was convinced had to be a drug addict on her set. In 2014’s Rudderless, another under-seen and equally acclaimed performance, his subtlety hits hard. Variety wrote, “Crudup does a lot to keep things watchable, playing with a slightly acidic wryness that suggests the character’s humor has only been heightened by his grieving hopelessness.” A.V. Club and Rolling Stone were just happy to see him strap on a guitar again for the role.

His work in myriad supporting roles (including Big Fish, Jackie, 20^th Century Women) is equally remarkable. But we’d venture that even if you’ve followed his work with the same enthusiasm we have, you still haven’t seen the half of it. Few actors at his level go as frequently and consistently between screen and stage. His theater credits number almost as many as his film roles and include a Tony win (among multiple nods). He’s a noted performer of Stoppard’s work, but our favorite pull-quote comes from Ben Brantley’s review of the comedically chilling The Pillowman: “Mr. Crudup’s finely chiseled features turn out to be ideal for registering the seductiveness, defensiveness and pure vanity of an artist.”

Whether or not Crudup would agree there’s mystery to what he does, he’s never been at pains to explain it. In many interviews, he comes across as a guy who just wants to be left alone to understand his characters and tell their stories as best and believably as he can, once telling The New York Times, “The truth is I don’t think actors should have to do anything but come in and act.” For the record, he loves what he does and feels grateful to do it, but you could understand his frustration with the entertainment press and its thirst for transparency. Do we really want to see the levers and pulleys behind a great performance, or would we rather sit back and enjoy being completely hypnotized by it? We’ll next have that pleasure when he shows up in Alien: Covenant, Justice League, and – after years of being pursued by TV casting directors – the new Netflix series Gypsy, opposite Naomi Watts.

Crudup says his hard-to-pin-down quality hasn’t always worked to his advantage in mainstream Hollywood, but then again, that’s never been exactly what he’s aimed for. And if flying below fame’s radar means occasionally having to reintroduce yourself to the business, so be it; he’s joked that his 50s will really be his decade. For the sake of our continued viewing pleasure, we hope he’s serious.