[s3e21] The Dead Pool -

A former Olympic champion and Zack's mentor. It is revealed Rob was a long-term steroid user; he killed Zack to prevent his secret from being exposed.

Zack Lindsey, a self-made champion swimmer on a partial scholarship. [S3E21] The Dead Pool

Zack's best friend; the two had been stealing cars together to help Zack afford basic necessities while training. Subplots & Themes A former Olympic champion and Zack's mentor

Castle brings along Alex Conrad , a rookie mystery novelist he is mentoring. Much to Castle's jealousy, Beckett takes a liking to Alex, even allowing him to shadow the investigation. Zack's best friend; the two had been stealing

Includes guest stars Justin Bruening (Rob Tredwyck), Brendan Hines (Alex Conrad), and Erik Palladino . Official Summary: View more on Apple TV or Rotten Tomatoes .

Zack was drugged with powdered chlorine and drowned in the UNY training pool. Key Suspects & Motives:

A rival swimmer who used undetected steroids supplied by the coach.