On Christmas morning, 1963, 15-year-old Kitty Doherty gives birth in a hostile Irish convent. Kitty knows her beautiful baby boy presents a huge danger to her family's Catholic community back in Liverpool's Four Streets. When her baby is adopted by a wealthy family in Chicago, Kitty considers the problem solved. But soon it's obvious the baby is very sick, and only his birth mother can save him. In Liverpool, things have begun to settle down. A charismatic new priest has arrived. The Dohertys are coping with the tragic consequences of Kitty's pregnancy, and the police seem close to solving the double murder which rocked the Four Streets to the core. But now all of that is about to be put at risk once more.