Grissom returns from his teaching sabbatical as Keppler tries to conceal his ties to a double murder case that he and his CSI colleagues are investigating.

Keppler desperately wants to keep his dark past hidden from his new CSI colleagues. As a result, he fails to disclose that he not only knows Frank McCarty (Cariou), the retired police officer who reportedly found the remains of his cop friend and a prostitute in the friend's Las Vegas hotel room, but that Frank may have had a role in the murders.

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