Eternal Sunshine of the Spotless Mind meets Ghost in this relationship indie from Tara Miele about a woman who is killed – or is she? – in a car crash. Sienna Miller is brilliant as gallerist Adrienne, who’s out on a date night (“it’s cheaper than couple’s therapy”) with her partner Matteo (Diego Luna) in Los Angeles. Frazzled and sleep-deprived from parenting their six-month-old Ellie, they’re bickering when their car hits an oncoming SUV.

At the hospital, Adrienne has an out-of-body experience, watching as porters cover her bloodied body with a sheet and push the gurney along corridors to the morgue. Next, she steps out of the hospital into scenes of the future without her: Matteo at her funeral, baby Ellie grown into a teenager.

Then Miele’s script yanks the rug away. Adrienne is at home, very much alive, a pharmacy of pills on the bedside table. It’s all been a dream. At least, that’s what everyone is telling her; she is concussed, disoriented. But Adrienne is convinced she’s dead. To help her make sense of what’s happening, Matteo suggests they relive the history of their relationship. But each brings their own resentment to the story, so the memory flashbacks change depending on who’s talking. As a couple, were they flawed from the beginning?

“It’s so sad we fell apart,” says Adrienne, but actually the love story is the least interesting thing here – it’s a bit generic and insipid. What’s really impressive is how Miele pulls off the tone shift from naturalistic portrait of a couple to psychological drama to moments with just an undertone of horror – in one, Adrienne, checking the cot, sees the baby stiff and lifeless, and becomes hysterical. From the confusion and alarm on Matteo’s face you know that she is hallucinating. It’s clammily claustrophobic.

Miller is at the heart of the film; her natural and believable performance touches so many emotions, and makes them all look so real. Adrienne can be funny about her condition. Watching a zombie movie she jokes: “These are my people.” But her terror of being pulled into nothingness is so convincing – which is quite a feat in a film that’s so contrived.

• Wander Darkly is released on 8 March on digital platforms.