Time is running out for Boyd as he fights for justice against a powerful adversary.
Boyd investigates the disappearance of 16 homeless boys from Waterloo Bridge in the 1980s.
Boyd needs Sarah's expertise to help expose the state's involvement in Barclay's death.
Boyd suspects a cover-up when a missing student's DNA matches with an unidentified corpse.
As the case continues, the squad investigate Murray using Grace as bait. However, when one member is shot and one member is arrested, the case could go in to turmoil, only for a connection to be revealed.
When the squad look in to the case of an army activist discovered in London's sewer system they discover that the case may have more police connections than they originaly thought.
The investigation into Claire Somers' death has seemingly unleashed a predator straight from the darkest childhood nightmare. But are they looking for a monstrous child-stealer, or misguided saviours?