02E02 - The Double Down

With the moon full, couples therapist, Ashley Cosway, is her husband, shot and words written on her face. When Castle, Beckett, Ryan and Esposito arrive and start to investigate, they get another call. Ryan and Esposito are sent to investigate the other murder. They find retired math teacher, Frank Anderson, shot in the park near his home. As both murders are being investigate separately, it doesn't take long before Castle has a bet with Ryan and Esposito on who can solve their case first. With evidence of restraining orders, infidelity, and rent-control and the only suspects each having an airtight alibi, both teams are at a lose. To confuse the matter even more, forensics indicates a mysterious link between the seemingly unconnected murders.