After being interested in the premise I added this film to my list and had forgotten that premise completely by the time I watched it, so I was pleasantly surprised that it laid its mind-bending credentials out appreciably piecemeal, making you as disquietingly confused as Ethan (Mark Duplass) and Sophie (Elizabeth Moss) are.

We meet the couple in marriage therapy, reminiscing in fond tones about the time they broke into a stranger's backyard for a midnight swim – the kind of crazy, romantic thing that's far behind them these days.

Their therapist (Ted Danson) suggests they play a concurrent note on a piano, wincing and telling them after they've done so that they're badly out of sync. How he knows that based on them playing piano notes is the first mystery, but he suggests they spend a weekend reconnecting, sending them to what seems to be an AirBnB the practice maintains or has access to for just that purpose (in real life, the property is star Ted Danson and his wife Mary Steenburgen's real life abode).

There's a main house and a guest cottage on the property, and after a slightly fraught first night when Ethan decides to sleep in the guest cottage the pair do find a tentative peace, ending up in bed together. But when Sophie returns to the main house she finds Ethan already there, fast asleep and with no idea about them sleeping together, apparently thinking Sophie is playing a prank on him.

After a few more false starts and confusing conversations, the strange and potentially terrifying truth becomes clear. Sophie and Ethan have perfect physical doubles that live in the guesthouse, both perkier, friendlier and more loving versions of the real pair that went for the weekend away to repair their relationship.

They're intrigued and decide to keep seeing their other partners, establishing rules about who's allowed to do what. But after the sci-fi set up, the human drama ensues, when both Ethan and Sophie find themselves more attracted to the double of their existing partner, finding them sexier and more loving than each other's original.

The script by Justin Lader isn't as interested in the strange science behind the presence of physical copies of people as it is the dark romantic hijinks that ensue so I didn't find the explanation behind the whole thing terribly satisfying (aside from not making much sense – the scene with the recordings on the computer is a good idea but doesn't explain much about it).

But until we get to that point there's an effective, Twilight Zone-esque style that takes its time unravelling.