The new series opens in dramatic fashion, when DCI Alan Oxford goes undercover to infiltrate a Manchester gang. But his true identity is known by them and they take him hostage. In one harrowing scene Alan is taped up from the neck down, with a strip over his mouth, and put in a coffin.

DS Tate infiltrates a gang of armed robbers, posing as the boyfriend of their getaway driver. But the closer he gets to the heart of the gang, the more the operations is threatened.

As three robbers make their getaway with £2.5 million worth of rubies, a second gang, disguised as the Flying Squad, takes the gems, and its leader, Frank McGrath, shoots the robbers. Scott is hampered by an officious lawyer and by McGrath's mission to exterminate his cohorts.

When DC Grace Harris falls into bed with a robbery witness, she ends up putting more than her heart on the line. The normally tough-as-old-boots copper endangers her career and her life when she falls for smooth-talking Francis Conte, who turns out to have all the charm of a rattlesnake.

Donachie's past comes back to haunt him in the shape of an armed robber he helped frame. The tables are turned on DC Ted Donachie when he's found with the loot from a bank raid. The plot thickens alarmingly when the real thief claims he was framed by Ted for a sex crime and is now taking revenge. So, apart from the affair he once had with colleague Grace Harris, what other skeletons is the strong, silent but looking-guiltier-by-the-minute Ted hiding in his closet?

The squad believes a multi-million pound robbery at a safety deposit centre could be an inside job involving the manager. A dangerous undercover operation pits the squad against Russian mobsters and forces DS Anna Dryden to confront the demons in her past.

The squad clashes with other departments when it arrests Dolan, at terrorist turned Special Branch operative. Tate becomes the scapegoat for a top secret MI5 operation and uncovers a career and life-threatening conspiracy.

There's a tragic twist in store as this tense police drama reaches a dramatic crescendo with the trial of evil Frank McGrath. The cruel hit man has launched a vendetta against DI Charlie Scott but it soon becomes clear that the detective's wife and child are also in danger from the villain. Charlie Scott's a dedicated copper but he's also a devoted husband and father, who would give his life to protect his family. Is that what he's going to have to do? After McGrath is found not guilty, Scott considers his future in the Met. He and Stephanie take a break in Cornwall, but they are pursued by McGrath.