Gates returns to rescue Arnott but leaves before Kate, her cover now blown, arrives to find evidence that a body had been stored at the warehouse. Arnott recalls that the chief torturer was called Tommy and admits to Kate that Gates saved him. She believes he is weakening in his attitude to Gates, whom he goes to see in secret, confirming his view that Gates is innocent of all the murders. Convinced that Gates is in danger but can bring the killers to justice Arnott persuades Hastings to let Gates set up a meeting with Tommy, recorded on a wire. Arnott and Kate intend to meet up with them but before they can do so Gates abducts Tommy to force a confession before committing an extreme act in the line of duty.

When three police officers are shot dead during the hijack of a seized drugs transport, AC-12 move in to investigate possible police collusion.

A fresh police leak enables another audacious raid, while Arnott's attempts to gather information put him in a dangerous situation.

As the hunt for H intensifies, Steve and Kate wonder if Hastings is guarding a dark secret.