Michael Dunnagan was never supposed to sail on the Titanic, nor would he have survived if not for the courage of Owen Allen. Determined to carry out his promise to care for Owen's relatives in America and his younger sister, Annie, in England, Michael works hard to strengthen the family's New Jersey garden and landscaping business.

Annie Allen doesn't care what Michael promised Owen. She only knows that her brother is gone—like their mother and father—and the grief is enough to swallow her whole. As Annie struggles to navigate life without Owen, Michael reaches out to her through letters. In time, as Annie begins to lay aside her anger that Michael lived when Owen did not, a tentative friendship takes root and blossoms into something neither expected. Just as Michael saves enough money to bring Annie to America, WWI erupts in Europe. When Annie's letters mysteriously stop, Michael risks everything to fulfill his promise—and find the woman he's grown to love—before she's lost forever.