England, 1919: Rose and Ivy board a ship bound for Australia.

One is travelling there to marry a man she has never met.

One is destined never to arrive.

Australia, 2016: Amongst her late-grandmother's possessions, Molly uncovers a photograph of two girls dressed in First World War nurses' uniforms, labelled 'Rose and Ivy 1917', and a letter from her grandmother, asking her to find out what happened to her own mother, Rose, who disappeared in the 1960s.

Compelled to carry out her grandmother's last wish, Molly embarks on a journey to England to unravel the mystery of the two girls whose photograph promised they'd be 'together forever'...