Detective Rob Ryan and his partner Cassie Maddox are assigned to investigate the murder of twelve-year-old Katy Devlin, whose body is found at an archeological dig site in the woods of Knocknaree, a quiet suburb outside of Dublin. What makes the case especially disturbing is that the crime scene is the same place where, twenty years earlier, Rob—then a boy named Adam Ryan—was found alone, his shoes soaked in blood, with no memory of what had happened to his two best friends, Peter and Jamie, who vanished without a trace. Despite the personal connection and the department's policy against officers working cases tied to their own past, Rob chooses to keep his identity secret and proceed with the investigation, believing he can maintain objectivity while possibly unearthing answers to his own childhood trauma.

As Rob and Cassie dive into the case, they uncover a tangled web of secrets involving Katy’s family. Her father, Jonathan Devlin, is a local politician pushing for development on the very land where his daughter was found. His campaign is mired in controversy, as protestors fight to preserve the historical site. The detectives begin to suspect that Katy’s murder may be linked to these disputes, but as they dig deeper, they find that the family’s dynamics are equally troubling. Katy was a talented ballet dancer, seemingly adored by her family, but her older sister Rosalind appears detached and chillingly unemotional about the loss. Their mother, Margaret, is a fragile woman, prone to nervous breakdowns, while Jonathan’s past reveals potential links to criminal activity and abuse.

As Rob becomes more deeply invested in the case, his personal demons begin to resurface. His memories of that fateful day in the woods remain elusive, but he is haunted by sensory flashbacks and fragments of emotions he can’t fully comprehend. Meanwhile, his partnership with Cassie, which had been built on deep trust and camaraderie, starts to unravel as he struggles with his own deteriorating mental state. Their once unbreakable friendship takes a darker turn when Rob, in his increasing instability, pushes Cassie away, leading to irreversible consequences for their relationship.

The investigation ultimately leads to shocking revelations, though not necessarily the ones Rob had hoped for. Katy’s murder is solved, but the truth about his past remains buried. The case closes, but not without casualties—Rob loses Cassie, his job, and the fragile grip he had on himself. In the end, In the Woods is as much a story of an unsolved past as it is of a solved present. The novel leaves readers with an unsettling sense of ambiguity, reinforcing the idea that some mysteries may never be resolved, and some wounds never fully heal.