On an eerily warm October evening in a suburb of Detroit, a new father and struggling fantasy novelist named McPhail gazes at a honey locust tree. The sight triggers a memory of the sudden, inexplicable death of Hannah, whom he loved when they were both fourteen. So begins a year-long odyssey, in which McPhail becomes obsessed with recollections of Hannah, puts his job and his marriage in jeopardy, and fears that his “obsolete consciousness” is spiraling into apocalyptic religious and ecological despair.