The Double Down

When two different murders fall towards the team, they are split between Ryan and Esposito, along with Castle and Beckett. Challenges are exchanged, and Castle wagers that he and Beckett will solve their case first. In each case, the results lead to an obvious suspect, each of which has an airtight alibi. When further evidence shows an odd connection between the two murders, unravelling the mystery will require the talents of all four.