Henry deals with a mysterious genetic condition that causes him to be repetitively and randomly ripped from his clothes and his present then transported to another time and place – naked and afraid.
It makes for a trying existence, and an even more complicated relationship with his wife Clare (Rose Leslie), who lives in standard linear time while encountering various versions of her true love at different ages.
Yet quantum-leaping drawbacks are even more visceral in the six-part series, kicking off Sunday (9 EDT/ PDT), in which Henry often vomits after arriving in a new time period.
"It's just another way to make this uncomfortable and jarring. Time travel is a superpower, but it's a horrible thing. It often makes Henry so unwell," says executive producer and screenwriter Steven Moffat. "It takes a magical dramatic device like time travel and grounds it in something real."
"It's not fun for Henry," says James, who got used to expelling the oat-based screen creation. "At least I didn't really have to make myself vomit."
James ("Divergent") gives further insight into Henry's raw reality:
This Henry is even hunkier than the OG movie 'Hulk'
Bana, star of the 2009 film version, starred as Bruce Banner in "The Incredible Hulk" a year earlier. He's no slouch in the muscle department. But it's even more clear that James' Henry is transporting himself to the gym between time-travel shifts.
The ripped origins are explained in the book. Henry is a naked survivor who has to immediately find clothes and outrun cops, who always seem to be waiting wherever he lands.
"Henry is good at running, stealing and fighting. To be good at those things, you have to be in a certain shape," says James, 37. "He's described as a panther, in a state of readiness and fearful all the time."
And the series shows a lot of Henry in various phases of his new (and nude) arrival. "Yeah, you see every inch of me," James admits, with only slight exaggeration.
Yet James insists he didn't go on a specific training regimen. "I just wanted him to look lean and mean," he says, joking that his impressive physique is helped by special effects. "It's all lighting and CGI."
Yeah, Henry's long hair is a wig
When James landed the part, he immediately grew his hair out to play the younger version of Henry. The look didn't go down well with his wife, actress Ruth Kearney. "She hated it," he says. "I looked ridiculous for months."
However, James found out on his first day on set that his hair had to go. He plays multiple Henrys of differing ages, sometimes in the same scene. Frequent hairstyle switches were required to show the changes and avoid confusion.
So 28-year-old Henry rocked a wig, while the 37-year-old Henry featured his regular cut.
"The wig makes me look vaguely OK," says James, "My long hair was much worse. I had my passport picture taken then with the hair and a mustache. The customs agent wanted to know if it was a mug shot. I looked criminal."
Henry desperately needs clothes, unless he can't be bothered
Most times, Henry's unclad arrival kicks off a desperate search for whatever clothes he can find. "He's completely devoid of anything, and that's dangerous," says James.
That can also make for unusual scenes, especially when Henry drops into very public places, like the "bean" sculpture in Chicago's tourist-filled Millennium Park.
"I kind of had to just grin and bear that," he says. "In the beginning, you're kind of chucking on robes and worrying about the in-between. But it's such a part of the story that, by the end, you're like, 'Let's just get on with it.' "
There's not much of a rush for covering when Henry arrives in front of his wife Clare.
"A guy who time travels and is used to that state is not going to be throwing on his clothes in front of his wife," says James. "It's part of the book, and we use that for comedy."
Those time landings were really hard
Keeping with the danger theme, Henry lands with a thud and audible grunt at different times and on varied painful surfaces: hard floors, rocks, car roofs, over stairs, on a highway, over hay bales, in a field full of cows.
James shared the landing duties with his stunt double but says "most were done by me. I really wanted that impact, to feel like it really hurt. I was covered in bruises. Landing on a car was particularly painful. I clipped my elbow and thought I'd broken my arm."
The falling is one thing, but the nude brawling that often followed for Henry is not something James ever got used to. "If I was in that situation in real life, I'd probably have the (expletive) kicked out of me," he says.
Whose dismembered feet were featured at end of episode one?
Sunday's episode ended with a toe-curling shock. A 28-year-old Henry wanders into an alley, assuming another Henry has just arrived.
Instead, he finds two frozen, dismembered feet, one with Henry's distinctive birthmark.
Henry has already made it clear that his misplaced body parts transport too, from ominous spilled blood to teeth. "All of me travels in time, even my nail clippings," Henry explained in the episode.
So the feet make clear that at some point Henry loses these crucial body parts. As Moffat says, "without his feet, Henry can't run." Henry needs to run.
Both the book and the original movie explore Henry's foot disaster, which takes away his ability to immediately run. The toe shot is a peek into his disturbing destiny.
"They're his feet," says James. "That's just a teaser for what's gonna happen in the future of the series."
There's still much more time. A freaked-out Henry mutters, "Not today, not today," to end the episode.
And he's right. Future "Time Traveler's Wife" series are planned even beyond this initial six-part series, even if HBO has not officially greenlit a new season.
"I'd say we've done about a third of the book," says Moffat of the current series. "There's a lot to come."
This article originally appeared on USA TODAY: 'Time Traveler's Wife': Theo James explains Henry's dismembered feet