One snowy night in 1998, Brooke Mulcahy's car slides off the road in rural Vermont. Her car is discovered. She is not. Twenty-one years later, Robert Kirby, Brooke's stepbrother, is paid a visit from a young woman (Lily), claiming to be Brooke's daughter. Since a tumultuous upbringing, Robert, formerly known as "Bobby," has enjoyed considerable success. Now an esteemed professor at a private Upstate New York university, Robert has just received a significant NEH grant. After Lily's visit, Robert's life is upended.

His wife Stephanie reveals she is unhappy in the marriage and takes their teenage son to visit her sister. Brooke's former best friend, Aaron Reardon, still devastated from Brooke's disappearance, offers to help. And forever lurking in the background is Mike Rakowski, Brooke's ex, a possessive, abusive drug addict.

As Robert's world unravels, he revisits that night twenty-one years ago where everything went wrong, unearthing a horrible, bone-chilling secret. In the vein of Simone St. James's Sun Down Motel, All Who Wander mines the depths of past transgression, begging the question: do past sin automatically negate future happiness?