資深剪輯師雪美蓮，總納悶自己到底姓史蒂芬，還是姓雪、姓陳？明明亞洲臉，又非混血，怎取洋人姓？一查不得了，父親竟來自澳洲！母親曾有文學夢，似還牽涉吳爾芙姪子的中國戀情？她化身偵探親自執導，翻找父親傳記、家庭電影、老照片，以「史蒂芬」為圓心，拼出一幅與世紀風雲、名人交織的私密家族史，追問殖民與身分認同。血緣纏如網，個體仍能重寫自我，乘故事翱翔。

Melanie returns to Hong Kong as filmmaker-in-residence at a university after living abroad for decades. She tries to redefine her cultural roots and affiliations, partly through the adventure of a tragic-comic romantic fantasy, partly through bonding with her young student Niki. Niki is making a documentary film with her mother about their family’s migration from China to their Hakka village in the New Territories. Melanie and Niki Both realise they are living with an original “molecule” that can’t be erased even after generations of dilution, the so-called “Memory of Water.”