On a small Greek island, a woman comes ashore with no memory of who she is, where she's from, or how she came to be shipwrecked there. As she's nursed back to health by the island's only inhabitants, four friends on an annual retreat, she detects tensions between the group that suggest not all is quite as it seems. Her new acquaintances each appear to be hiding something --- something that may relate to the mystery of her identity. Meanwhile, in a pretty suburb on the outskirts of London, Eloise vanishes into thin air. Her husband, Lochlan, is desperate to find her --- but as the police look into the disappearance, it becomes clear that Lochlan and Eloise's marriage was not the perfect union it appeared.