It is all change in the clandestine world of MI5 when new agent, Adam Carter, joins the team. Tom has been branded a traitor and has disappeared, while Harry is in hospital, seriously wounded, and there is dissension in the ranks. Danny and Zoe seek to clear Tom's name despite the fact he appears guilty and may even be dead. Will Tom, missing since shooting Harry, re-emerge to prove himself an innocent victim of a set-up? And will former MI6 agent Adam Carter, the new edition to the team, provide the drive and enthusiasm so apparently missing? If his track record and the reputation that precedes him are anything to go by, there are going to be plenty of fireworks.
Tom Quinn has disappeared after shooting his boss Harry Pearce. He also stands accused of assassinating the Chief of Defence Staff. Chairman of the Joint Intelligence Committee Oliver Mace uses this a pretext to launch a punitive investigation of MI5. Zoe, Danny and the team must prove Tom innocent and save the service from government takeover.
Harry reawakens sleeper agent Fred Roberts, a renowned chemist and family man. As Fred becomes more deeply involved with deadly terrorists, Tom has a crisis of conscience which could jeopardise his career.
The latest round of Middle East peace talks are abruptly halted when a key delegate is killed. With the peace process derailed MI5 starts to investigate a newspaper mogul and renowned Israeli extremist, and a group he's associated with called the November Committee. Can MI5 prevent an assassination attempt on a pro-Palestinian British MP?
Saturday morning. Danny and Colin practice their firing technique on MI5's gun range. Zoe and her fiancé Will are still madly in love. Ruth watches old movies at home whilst longing for real-life romance. A North Sea mission places additional stain on all relationships...
While a deadly hacker turns Britain upside down, Danny decides whether to reveal all to Will, MI5 hunts the source down to an Islamic mosque with the help of MI5's best computer programmers. But things get suspicious when Ruth, close onto the tail of the hacker, goes missing and so does a member of the special team...
The baby of a celebrity couple is kidnapped and they call in MI5. Fiona goes in undercover to gather more information about the couple against Adam's wishes.
When known mercenary Robert Morgan is spotted at a top-secret disused Soviet arms dump, he obviously has to be brought in for questioning. Is it all right to blackmail innocent people to get the information you want? Is it acceptable to threaten the lives of a suspect's family?
It's Fiona's birthday, and she's not going to forget it! While inspecting a possible Islamic terrorist safe house, they are kidnapped. With the threat of his son's, his wife's and Danny's life, Adam must choose who won't live to see another day, Fiona or Danny? The prime minister's life is in danger. Will MI5 give into the kidnappers demands? But then to everybody's surprise... Danny makes the ultimate sacrifice.