In 1751, Johannes Christian Welde sailed from an island in the English Channel to America. Two hundred and fifty years later, Natalie Welde boards a plane bound for the country her ancestor left behind. But for those intervening years, their paths might have crossed—she on a Delta plane flying at 38,000 feet, he in steerage on a ship bound for America. Natalie's brother, Billy, dreamed of visiting the land of his ancestors, but it was never possible. Though he always greeted life with optimism and humor, the suicide of his son, the chill of his home life, and the ravages of time had taken a toll. Billy is in hospice care when he learns of Nattie's planned trip to Europe. He asks that she bring him a worry stone from the river his ancestor traveled—from Heilbronn to the North Sea. After landing in Amsterdam, Natalie and her husband, Hank, board a cruise ship that travels up the Rhine, retracing Johannes' journey in reverse. While Johannes endured storms, sickness, and danger on the timber raft floating down the Rhine, Natalie's ship sails peaceful waters. Yet she is haunted by the tragedy of her brother's life and her desire to fulfill the promise she made to him.