Johnny Worricker is a long-serving MI5 officer. His boss and best friend Benedict Baron dies suddenly, leaving behind him an inexplicable file, threatening the stability of the organization. Meanwhile, a seemingly chance encounter with Johnny's striking next-door neighbor and political activist Nancy Pierpan seems too good to be true. Johnny is forced to walk out of his job, and then out of his identity to find out the truth.

Worricker after the director of MI5 dies. A conspiracy to turn control of MI5 over to the Prime Minister leads Worricker to the islands known as the Turks & Caicos, where he is persuaded by the CIA to deal with a group of ambiguous Americans attending a high-level conference. At the same time, an old girlfriend, Margot Tyrrell, is being asked to betray her boss in London in order to establish an illicit connection between the prime minister and dark...

The group was left reeling after the shocking death of Danny at the hands of hostage-takers as the last season concluded. Now Adam, Harry, Ruth, Fiona and rising star Zafar set out to become even stronger in their battle to safeguard the nation.

The acclaimed detective series returns with three new mysteries set in the uncertain days at the beginning of the Cold War.

The Cold War heats up when a KGB defector exposes Operation Glass, a potentially devastating Soviet plot to activate sleeper agents across the UK. The charismatic but paranoid head of MI-5, known simply as 'Daddy', assembles a secret committee of spies and intelligence officers to investigate. They're the only colleagues he trusts in a world of double agents and lies, but has he chosen well?