Tasha has always felt in the shadow of her older sister, Alice. Their lifestyles couldn't be more different; Alice is married to wealthy entrepreneur Kyle and has a high-flying career, Tasha is married to her childhood sweetheart and lives in a Bristol suburb with their four-year-old twins. When Alice realises that Tasha is struggling - with money, the kids, losing her identity - she suggests they do a lifeswap for a week. Alice and Kyle will come to stay at Tasha's terraced house to look after the twins, while Tasha and Harry spend the week in Alice and Kyle's Venice apartment. But a few days in, it all goes terribly wrong. Tasha receives a phonecall to say Alice is in hospital and Kyle is dead after an intruder broke into their house. They think it must have been a burglary gone wrong. Until a note arrives through the letterbox. Who was there that night?