Marisa Hagen discovers her husband has had multiple affairs throughout their marriage, but the possible existence of an illegitimate child could save the life of her son, Jack. Jack needs something only a sibling can provide: a perfect match. So her search begins and, before it ends, she finds both a new man for herself and a new beginning for her son.
Life seems idyllic for Marisa (Jacinda Barrett) and her son, Jack (Tom Russell), until a poor performance at a school soccer match ends with Jack in the hospital and Marisa trying to find her husband, David (Richard Roxburgh), who is away at a conference. In fact, David is planning to leave Marisa for his current mistress (Yvonne Strahovski), with his phone off and not a care in the world.
Jack is diagnosed with leukemia and the only possibility of a cure is if David has had a child from one of his many flings who could be a bone marrow donor. So Marisa looks back through his diaries, figures when he could have been having affairs, and goes out door knocking. Unsuspecting women face a desperate mother as Marisa searches high and low for possibilities – and the full scale of David’s infidelity is revealed.
Meanwhile, Jack befriends Finn (Kodi Smit‐McPhee), a young Irish boy in the next bed. He has been traveling the world with his father, Connor (James Nesbitt). Initial disdain turns to mutual respect as both Marisa and Connor find their own ways to deal with their sons’ illnesses.