As the small-scale puzzler "Coherence" brings four well-appointed couples together for a dinner party on the night of a rare astronomical event, the prevailing expectation of writer-director James Ward Byrkit's film is that something disruptive will happen beyond the usual relationship tensions: exes in the same room, professional jealousy, snarky comments.
Then the lights go out, cellphone screens crack, neighborhood explorations are made and the chitchat turns tensely philosophical when evidence suggests an unimaginable possibility: a co-existent reality — same dinner party, same partygoers, different timeline — just down the street.
Byrkit's parlor game of a movie is in certain ways a tart sci-fi satire of bourgeois hang-ups like identity neurosis and regret. There's some "Memento"-ish fun in navigating the characters' tricky plans to keep their timeline safe from now-feared doppelgangers.
But the real test of a gimmicky movie like "Coherence" is whether the players' emotional lives can stand on their own without simply being fodder for a fun-house experiment, and it's here where the movie falls short. But only slightly.
The performances — notably from Emily Foxler, the closest thing to a protagonist, and "Buffy the Vampire Slayer" alumnus Nicholas Brendon — are solid, and the conceit is alluringly mind-bending without ever seeming off-puttingly brainy.
No MPAA rating.
Running time: 1 hour, 29 minutes.