Merry lives a simple life. For work, she writes cryptic crossword puzzles. For pleasure, she swims in the icy cold sea. And in between she keeps a careful eye on her neighbour, Lucas Manning, the son of her late best friend Julia.

One day Lucas's wife reports him missing. Merry has known Lucas his whole life; he would never walk out like this. Bad things have always hovered around the Manning family. Lucas's abusive criminal father disappeared decades ago, and his brother Sean is in jail. But Lucas is different. A good man. He was the one who turned Sean in to the police, after all. Although Sean has spent every day since professing his innocence.

As she begins to dig into Lucas's life, Merry forms an uneasy alliance with a private investigator doing the same. Gareth was hired by Lucas's employers, who are also desperate to locate him - and the sensitive work project he has absconded with. Merry might be a cryptic crossword mastermind, but reading people is hard. Was she wrong about Lucas? Did the wrong brother go down all those years ago? This is no straightforward disappearing act: something much more sinister is at play. But as she get closer to the truth, Merry must confront her own dark past with the Manning family, which she has fought so long to keep buried. Who can she trust with her secrets?