“Faithfully Yours” is a Dutch thriller about wives who cheat and what the almost-as-dishonest mistrusting men who married them might be capable of if they find out. It’s a subtly-acted slow-starter, with a fine, flashy finish, a “solid” genre piece that never quite crosses over into riveting.

Bracha Van Doesburg plays Bodil, a no-nonsense domestic court judge who lives for her weekend’s away from it all. Or so we gather.

She’s got a little boy she dotes on and a husband who indulges (Nasrdin Dchar) her getaways. They drop her off at the train station, and we start to figure out something is up.

She and her pal Isabel (Elise Schaap) go over their elaborate schedule for this little Belgian (Ostend) get away. But as they pass intructions over this lecture, that play, etc., they share burner phones. They discuss timing, places where “I’ll do your social” media while “I’ll be seen” here.

They’re plotting their latest little “fling.” Or “flings.” They’re supposed to be in the beach house Bo inherited from her aunt. But Isa checks into a hotel, bedazzles herself and hits the club for a little easy interaction and uncomplicated intercourse.

Bo? The judge who decides who is “fit” to have child custody, and the like? She picks up strangers, including the somewhat famous “philosopher” (Matteo Simoni) who gives a talk about how “To Lie the Truth” which she attends.

It’s all modestly kinky right up to the moment Bo comes in from a swim and finds a bloody crime scene — with no body — in the beach house.

Yes, she calls the cops. No, she doesn’t tell them the whole truth, or really much of it all. The blood was Isa’s, and when her clingy and neurotic novelist husband (Gijs Naber) and Bo’s other half Milan show up, keeping her story straight with each of them, and with the leery lady cops (Sofie Decleir and Anna De Ceulaer) is going to be a challenge.

When will she have the time to figure out what’s happened to her friend, and if it was something awful, whodunit?

Director and co-writer André van Duren — “The Fury” and “Gang of Oss” were his — doesn’t get all the paranoia he might have wrung out of this material and Doesburg’s performance of it. Bo doesn’t seem much more than puzzled by all this confusion, all the fingers pointing in this or that direction.

If this poker-faced turn is meant to keep the viewer confused about what she’s confused by, and what she might be in on, it doesn’t allow for much viewer investment in the character or rising suspense in fear for her fate.

We never get a hint that she’s frantic to keep her secret, and her friend’s, never fret when she’s a suspect, when the menfolk seem to start figuring out what’s really been going on during these junkets to Belgium.

That softens the impact a bit when the film’s third act starts to deliver some real punches.

Still, “Faithfully Yours” is mysterious enough and thoughfully plotted enough to hold one’s interest. I know it held mine.

Rating: TV-MA, violence, sex, profanity

Cast: Bracha Van Doesburg, Elise Schaap, Nasrdin Dchar, Gijs Naber, Matteo Simoni, Hannah Hoekstra, Anna De Ceulaer and Sofie Decleir

Credits: Directed by André van Duren, scripted by  Elisabeth Lodeizen, Paul Jan Nelissen and André van Duren. A Netflix release.

Running time: 1:36