A champion swimmer and Olympic hopeful is found dead in a pool, suffocated by a rag and left to drown. Castle and Beckett discover the victim is from a tough neighborhood, which helped him steal cars to pay for tuition. After tracking down leads through an ex, coach, and teammates, the detectives find themselves stumped after discovering steroids in the victims apartment.
The victim had caught a teammate with the steroids and was confused on what to do. He approached a friend and former competitor about the situation. The friend had also used the designer steroid during his competitions and was afraid of being found out. The steroids had come from their common coach. To prevent being found out and being stripped of his awards, former competitor and friend Rob killed the new Olympic hopeful.
Castle is mentoring Alex Conrad, a new mystery writer. Rick gets jealous over the relationship Conrad forms with Beckett. He invites him to poker night where Michael Connelly and Dennis Lehane appear. Castle admits to Beckett that he is jealous; she responds that it is sweet and he has no worries.