First broadcast 18/19 July, 2004.
When the body of a suspected terrorist is found in the stolen car of a former Home Secretary, Boyd and his team soon find themselves involved in the shadowy world of the Security Services.
Notable guest stars: Oliver Cotton, Frances de la Tour, Timothy West (father of Samuel West).
The one where… Boyd calls Grace “Gladys”.
First broadcast 23/24 October, 2005.
When new evidence connected to the 1988 Cherry Tree Farm murders comes to light, both Spencer’s prior involvement and the close connection of one member of the CCU team to Commander Will Drake of the ATO make reinvestigating the case a very dangerous gamble.
Notable guest stars: David Calder, Mark Lewis Jones.
The one where… Felix is injured when a bomb goes off in the CCU’s squad room, and Spencer gets shot.
First broadcast 14/15 January, 2007.
Trying to avoid a diplomatic incident, the Foreign Office task the CCU with finding the skull of the Mahdi, which was taken as a war trophy in the 19th century. In a parallel investigation, the team try to identify the murderer of Omar Jaffiri, who was allegedly tortured on behalf of the British security services.
Notable guest stars: Graham Crowden.
The one where… everyone spends an awful lot of time looking at skulls.
First broadcast 27/28 March, 2011.
When the body of Piers Kennedy, an ex-serviceman turned peace campaigner, is found in the sewers close to the Houses of Parliament, Boyd is quickly visited by MI5. He is warned not to share classified information with Grace, who was once on a government watch list. Things get more complicated when it seems that one of her former lovers, Murray Stuart, was somehow involved in the events that culminated in Kennedy’s disappearance.
Notable guest stars: John McArdle, Jack Shepherd, Penny Downie.
The one where… Grace’s activist past is revealed, she gets injured going to meet Murray at Boyd’s insistence, and new team member Sarah Cavendish sets Boyd’s downfall in motion.
First broadcast 3/4 April, 2011.
The team investigate the strange death of Karl Barclay, a university student who converted to Islam. Suspecting the involvement of the security services, Sarah meets up with a contact from her days in counter terrorism. When Boyd is abducted, beaten, and left to die in an empty warehouse rigged with explosives, it becomes clear that there are people in high places who don’t want the truth about what really happened to Barclay to be revealed.
Notable guest stars: Don Warrington, Ashley Chin, Clive Wood.
The one where… an angry Boyd headbutts his gloating captor in the face, and more of Sarah’s backstory is revealed after she saves his life.