One of the hundred books a year I read:

FBI agent Rob Barrett has spent most of his young career studying interrogation behavior, so he jumps at the chance to put his academic knowledge to work interrogating a drug addict about her involvement in the disappearance of two young people in her town. Months of work leads to a payoff moment when she confesses to being an accomplice to murder.

The detail in her story is compelling and a local man with an upstanding reputation is implicated in the crime. To prove the case, the police dig for corroborating physical evidence while the town gossips about the crime.

That evidence, however, disproves her story leading to the disgrace of Agent Barrett and disaster for local police. The FBI agent is transferred to a remote posting and his career becomes quite limited. Despite all warnings to stay away, he remains obsessed with the case and the confession he extracted. If the crime did occur the way it was described, how did it happen?