Low on inspiration for his second book, a gloomy novelist agrees to write a memoir for a dying man — and swiftly becomes part of his bloodstained past.

Five friends return home from a marriage in Canada to the United States. Not far from the border, two customs officers stop them to check their identity.

Paul Diallo, a history teacher, lives a quiet life with his wife and kid. During summertime, he lends his house to his son’s babysitter and her boyfriend. When they return,…