In the summer of 1914, the transatlantic ocean liner carrying Grace Winter, 22 and her new husband Henry suffers a mysterious explosion. Forced into an overcrowded lifeboat, newly widowed Grace Winter battles the elements and her fellow survivors and remembers her husband, Henry, who set his own safety aside to ensure Grace's. The survivors quickly realise the boat is over capacity. For any to live, some must die. As the castaways battle the elements, and each other, Grace watches and waits. Her journey to a life of glittering privilege has been far from straightforward, and now it is in jeopardy. Over the course of three perilous weeks, the passengers plot, scheme and console one another while sitting inches apart. Their deepest beliefs about goodness, humanity and God are tested to the limit as they discover what they will do in order to survive.