“American Star” is a nice surprise. To hear it described, its premise sounds almost ridiculously predictable: Ian McShane as an old hit man on his last assignment. But the movie turns out to be a serious work that goes to unexpected places.

Director Gonzalo López-Gallego (“Backdraft 2”) isn’t interested in making a point with this story so much as he is in creating a mood, one that could be described as meditative and humane. Throughout the film, McShane’s face suggests sadness, some regret and even suppressed longing, but there’s an implacable hardness there, too. McShane, most recently known for starring in the “John Wick” franchise as well as the HBO series “Deadwood,” is not a sentimental actor, and “American Star” is an unsentimental, somber film, with occasional eruptions of realistic and disturbing violence.

At first you might think the setting is New Mexico or Arizona, with its vistas of desert and mountains. In fact, it takes place about 5,000 miles from there, in Fuerteventura, one of the Canary Islands. A taciturn man who calls himself Wilson (McShane) has been sent there to kill somebody, but the guy is out of town and won’t be back for a few days. So, lacking anything else to do, Wilson acts like he’s on vacation, enjoying shows, dinners out and drinks at the bar.

In the bar, he strikes up a conversation with a young bartender, Gloria (French actress Nora Arnezeder), and their emerging relationship becomes a big part of the story. The relationship’s fascination is that it’s hard to pin down. There’s definitely a male-female dynamic going on, but she’s about 30 and he’s a lot older than that (at least 75, judging from some of the things he says, and that’s reasonable, as McShane himself is currently 81).

Whatever’s going on, it’s clear that Gloria appreciates him as a man, and as a certain kind of man, and yet can’t quite place him — not in the friend zone, or the potential boyfriend zone, or the daddy zone.

McShane’s innate qualities as an actor flesh out the role he’s playing. Wilson is supremely self-controlled, but not walled off to feeling, and he has an appealing mix of confidence and curiosity. He doesn’t take much seriously, and that includes himself. Occasionally a funny look crosses his eyes, in which he registers the absurdity surrounding him.

McShane does not do what you expect, which is to play the hit man as having been destroyed by his work. He plays him as having been isolated by it. But that isolation isn’t complete or impenetrable, especially at this stage of his life.

Lopez-Gallego and screenwriter Nacho Faerna slowly build the relationship between Wilson and Gloria. This gives Arnezeder an opportunity to show this woman from a number of sides — as someone charming but also a mess, a grown-up with a grown-up’s problems and a teenager’s impulses.

Fellow French actress Fanny Ardant (“Callas Forever,” “Roman de Gare”) makes a strong one-scene appearance as Gloria’s mother, in a scene in which mom, Gloria and Wilson have lunch together. Like a lot of “American Star,” it’s interesting because of what we see and what we don’t. Gloria has orchestrated a meeting between two very good-looking old people; is this a fix-up, or just a casual lunch? Or maybe this is just an undefined meeting, the kind of hanging out that people do in hot weather, when they’re far from home.

The title of “American Star” refers to an American cruise ship that was christened in 1939 and shipwrecked off the coast of Fuerteventura in the 1990s. In real life, it’s no longer visible, but in the film, it’s a haunted, forlorn presence off one of the island’s coasts and seems to stand as some kind of metaphor for Wilson.

Fortunately, the metaphor isn’t specific. It’s just a wonderful wreck that you want to keep looking at.

Reach Mick LaSalle: mlasalle@sfchronicle.com