Eight years after Arthur Penhaligon disappeared on Blackwood Ridge and was declared dead, he walks into the home he shared with his wife, Claire—unchanged, carrying his backpack, and convinced only hours have passed. Claire, now married to Greg, must confront the return of the man she mourned while protecting her rebuilt life. Greg struggles to defend his marriage against a rival he cannot hate; Arthur has returned to a world that continued without him.
 
As watches run backward, photographs change, and silver fog begins invading the house, Arthur’s return becomes connected to Ephraim Vale, a nineteenth-century traveler who vanished on the same trail and returned eleven years later. With the help of historian Miriam Bell, the three discover that Vale also came home to find his wife, Abigail, remarried—and that his refusal to accept her new life unleashed a temporal force that ultimately robbed her of the ability to remember loving either husband. Claire realizes that the supernatural threat is attempting to impose the same cruel choice upon her: erase her former life with Arthur or sacrifice the present she shares with Greg.