Alison has just married Australian Sean Weston. Both of their children struggle with the new family situation, and Alison's former husband wants her back. When Sean disappears during a morning surf, it is not clear if he got caught up in a rip tide or if there is more to his disappearance.

Determined to fulfill his life’s mission, 26-year-old John Allen Chau embarks on a dangerous adventure across the globe to convert the uncontacted tribe of North Sentinel Island to Christianity, while a detective from the Andaman Islands races to stop him before he does harm to himself or the tribe.