Would you grab any chance at happiness, even if it wasn't yours to take? 1926. On a remote island off Western Australia, Tom and Isabel Sherbourne - a young, childless couple - run the Janus lighthouse. Life is quiet, cocooned from the rest of the world, but when one April morning a boat washes ashore with two bodies inside - an infant and a dead man - the path of their lives suddenly hits an unthinkable crossroads. Compelled by Izzy's desperate pleas and the pain of their own recent stillbirth, Thom finds himself buyring the stranger's corpse while his wife eagerly pulls out her, as yet unused, book of babies' names... Having rashly decided to keep the child and pass her off as their own, a rift opens in their relationship, which is tested to the limit when two years later they return to the mainland and are reminded there are other people in the world. And one of them is looking for her baby...