“Marlowe” is a strange case. It’s not a terrible movie, but a terribly misbegotten one, off in all its details. This is the work of a reasonable, intelligent director, Neil Jordan (“Greta,” “The Crying Game”), who had a bad idea and then compounded it with wrong choices and crazy casting.

We’ll start with the source: The movie is called “Marlowe,” but it’s neither based nor directly inspired by any of Raymond Chandler’s Philip Marlowe novels. Rather it’s an adaptation of “The Black-Eyed Blonde” (2014), a Marlowe novel by the Irish novelist John Banville.

As such, the movie is a kind of amalgam of various elements from the Chandler novels — a Frankenstein of once-living parts, assembled into a structure in hopes of a lightning strike that never happens.

Then there’sLiam Neeson.Love the guy, but a 70-year-old Philip Marlowe? This is how you know you’re too old to play a detective in a movie set in 1939: If every time you smoke a cigarette, everybody in the audience worries that you’re going to die, you’ve been miscast. At crucial points in the story, when I was supposed to be rapt and engaged, I was thinking, “I hope they’re clove.”

What’s worse, the fight choreography makes Neeson look even older. There’s really no excuse for this, because we know, from recent movies (“Honest Thief,” “Memory”), that the big guy can still do action. But here, when he initiates a fight by kicking over some furniture, Jordan doesn’t use quick cuts to convey velocity. Instead, he shows Neeson slowly lifting his leg and kicking the furniture like any mere mortal.

Like a lot of film noirs, “Marlowe” begins with a beautiful woman walking into a Los Angeles detective’s office. Diane Kruger plays Clare, looking for a lover who has gone missing. For the rest of the movie, Marlowe and Clare are supposed to be attracted to each other, but we are also made to understand that this is something that shouldn’t happen. “I’m twice your age,” he intones.

But really? Is he supposed to be 90? There’s a 24-year age gap between Neeson and 46-year-old Kruger. If the gap were 35 years, it would mean one thing; 10 or 15, and it would mean another. But while casting a woman in her mid-40s opposite Neeson may not be the usual age spread, it’s not beyond the pale.

Then there’s the movie’s look. The interiors of “Marlowe” were shot in Ireland, and the exteriors were shot in Spain. No surprise it doesn’t quite feel like Los Angeles. But then, Jordan isn’t going for realism, but a dream-like, colorful, amusement-park, fantasy Los Angeles, which is beautiful in its own right but doesn’t support the story.

With the exception of Jessica Lange, who tears into her fairly brief role as a wealthy and wicked former movie star, everyone in “Marlowe” is directed as if to seem groggy with depression. It’s as if they’re all bored with the story before they tell it, and then they tell it while trying not to fall asleep.

Compounding the languidness of the cast is the dreamy soundtrack, which filters underneath scenes — even ones of supposed tension, as if to say, “Yeah, none of this really matters.” If they don’t care whether Marlowe finds this guy, why should we?

By the end, Jordan pivots and tries to offer “Marlowe” as a commentary on film noir, or Hollywood, or Los Angeles, or noir in Hollywood. Trust me, it’s a commentary onsomething,but it’s so far removed from Hollywood — from America and from any source of inspiration — that it really has nothing to say.

Reach Mick LaSalle: mlasalle@sfchronicle.com