When a terrorist escapes custody during a routine handover, Will Holloway must team with disgraced MI5 Intelligence Chief Harry Pearce to track him down before an imminent terrorist attack on London.

The elite team from the clandestine security service, MI-5, tackles organized crime, terrorist activities, anarchists, and more.

Johnny Worricker and Margot Tyrrell as they are on the run across Europe, with MI5 hard on their heels. But life in exile is proving much harder than either of them expected. Worricker knows that his only chance of resolving both his personal and his professional lives is if he returns home to confront the powerful prime minister, Alec Beasley. In a duel of wits between the two men, there will be only one winner.

The threat to national security increases and the need to thwart the activities of terrorists operating within the UK becomes more urgent.

The penultimate season of the hugely successful, long-running drama introduces a host of new characters. There's Beth Bailey, a brilliant ex-mercenary who was posing as an Eastern European prostitute when she ran into the team. Dimitri, an ex officer in British Special Forces, has been recruited for his skills in fighting terrorism on the front line. And finally, data analyst Tariq has been fast-tracked through the system.

Having spent years in a Russian prison, Lucas North is welcomed back by MI-5 supremo and old friend Harry Pearce, who was instrumental in finally securing his release. Lucas is keen to get back to work straight away and, with Section D's current priority operation having a strong Russian connection, he could well prove invaluable. But, after so many years with only a high ranking Russian spymaster for company, can Lucas's loyalty really be taken for...

When an M15 officer unveils a scandal that poses a threat to the government, he must risk his life in order to find out the truth; Johnny Worricker and Margot Tyrell are on the run across Germany, but Worricker knows his only chance of solving his problems is to return home to England and face his nemesis, the prime minister; Johnny Worricker is hiding out from his work at MI5 in Turks and Caicos and must work with a financial public relations specialist...

Worlds collide and nothing is what it seems in the thrilling new installment of MI-5. While Tom has been branded a traitor, and Harry is in the hospital, an enigmatic agent, Adam Carter, has been recruited from MI-6 to help pick up the broken pieces.