Sylvia and Paul's marriage seems perfect: she is beautiful, spiky and clever, he is a devoted husband and father to their two young children, Megan and Jude. When Sylvia is diagnosed with terminal cancer at 38, she knows she must help Paul navigate family life without her - and finally tell him the secret she has kept throughout their marriage. She writes a manual: a guidebook to their shared domesticity. As Paul learns to survive without Sylvia, he realises the extent of her legacy and finds himself indebted to her once more, for saving them from an even greater tragedy.