It's the week before Christmas and the cathedral city of St Albans is blanketed by snow and wreathed in pretty lights. But this scene of beauty and harmony is shattered when the body of a local girl is found in a frozen lake.

The police, led by fraught Dutchman DCI Jansen, are at a loss. Their only lead comes from the dead girl's neighbour, Jenny. She claims she's had visions of what happened the night the girl went missing. But Jenny is a sleep-deprived new mother, whose midnight wanderings pull her ever closer to the lake. Can Jenny be believed? Is she implicated?

Then another girl goes missing, and the tight-knit community unravels. Neighbour turns against neighbour, and Jenny has no idea who to trust. As Christmas Eve approaches, and the police race to catch the killer, Jenny discovers a secret about her past – and why she could be key to everything...