Desperate Hearts tells the story of Katherine Summers and her three sisters growing up in London's East End in the 1960s, where their violent father is caught up in the gangland world of dodgy deals, murder and the notorious Kray brothers. Times get tough, Katherine's father forces her mother into prostitution, and the family falls apart when her mother goes into hiding and the four little girls are placed in institutional care.But with the support of each other and help from an unexpected source, Katherine and her sisters gradually rebuild their lives, ending their school days in an exclusive girls school. Then, on St. Valentine's Day 1974, from an upstairs window, Katherine witnesses her father shoot her mother's lover dead in the street below.