Castle returns to the City of Angels in search of answers about his missing time. But things take a deadly turn when he's recruited by the legendary Greatest Detective Society to help solve a murder.

A clue at the scene of the death of an armored-car driver leads Beckett and Castle back to an old case solved by Esposito. But complications arise when they learn that Esposito might not have been telling them everything about his past with the culprit.