In some numbering formats, the second episode of Season 2 is listed as the 15th overall episode (Episode XV) of the series. This episode is titled (or simply the continuation of the Chroma Conclave arc).
A therapist is found drowned during a couples' retreat. While all four clients have alibis—they were having dinner together at the time of the murder—each briefly stepped away, making everyone a suspect. [S2E2] Episode XV
Castle: Episode 2x15 Suicide Squeeze: scriptline - LiveJournal In some numbering formats, the second episode of