Gangs are a major problem for police in at least 20 of London's 32 boroughs. Detectives Stuart McNaughton and Bob Dolce work for Trident, the Met's specialist gang unit. As increasingly younger boys and girls are being lured into the gang lifestyle, Bob and Stuart have focused on London's most dangerous gang, working undercover to take down its leaders and stop the lucrative drug trade thriving on the streets of south London. Wealthy residents of Camden, north London, have been plagued by a wave of violent snatch-and-grab thefts by robbers using mopeds to evade police. Suspects are often only in their teens and cops are discouraged from chasing the criminals. Public confidence in the police is running low, and it's up to borough commander Richard Tucker to win back local trust and wipe out the problem. Police constables Tim Dawes and Steph Mills have been patrolling the streets of Brixton for over five years and deal with knife crime on an almost daily basis. But nothing can prepare them for the shock of a vicious knife attack in broad daylight. It's up to them to try to save the life of an innocent teenage boy.