Pop star Lulu has always wanted to get to the bottom of a family mystery. She knows that her mum, the middle child of seven, was the only one to be given up by her birth parents and raised by another family, but she has no idea why. Lulu travels home to Glasgow, where she uncovers the real-life Romeo and Juliet story of her Catholic grandfather and Protestant grandmother's love affair across the city's strict sectarian divide. Digging deeper, she discovers some dark secrets about her grandfather's past which force her to reassess what she thought she knew about her mum's story.