"Susi Holliday is one of our best and most original creators of tense and twisty tales." -Ian RankinFour hikers enter the mountains. Only two return. But is it tragedy? Or treachery?When sisters Cat and Ginny travel with their husbands to the idyllic Swiss Alps for a hiking holiday, it's not just a chance to take in the stunning scenery. It's an opportunity to reconnect with each other after years of drifting apart-and patch up marriages that are straining at the seams.As they head into the mountains, morale is high, but as the terrain turns treacherous, cracks in the relationships start to show. With worrying signs that someone might be following them, the sun begins to set and exhaustion kicks in. Suddenly, lost high on a terrifying ridge, tensions spill over-with disastrous consequences.When only two of the four hikers make it down from the mountain, the police press them for their story-but soon become suspicious when their accounts just don't add up.What really happened up on that ridge? Who are the survivors? And what secrets are they trying to hide?