Mum-to-be Rachel did everything right, but it all went wrong. Her son, Luke, was stillborn and she finds herself on maternity leave without a baby, trying to make sense of her loss. When a misguided well-wisher tells her that 'everything happens for a reason', she becomes obsessed with finding that reason. She remembers that on the day she discovered her pregnancy, she'd stopped a man from jumping in front of a train, and she's now certain that saving his life cost her the life of her son. Desperate to find him, she enlists an unlikely ally in Lola, an Underground worker, and Lola's six-year-old daughter, Josephine, and eventually tracks him down, with completely unexpected results...