Perez and Tosh board the dive boat to investigate this latest death. Was this a tragic accident, or was the only witness to Galbraith's murder silenced before they could speak? Suspicion falls on Mick Muir, the Life Support Supervisor responsible for diver safety - and when he is attacked by angry crew members, he has to be rushed to hospital. Perez senses the hand of organized crime, but getting answers proves difficult.