Spooks, The Extremist

An operation to assassinate a suspected terrorist in Tehran fails to kill its target and leads to the release of a lethal virus in Britain.

With Britain on the verge of a plague epidemic, the team must find a vaccine quickly. Harry orders the interrogation of spies from all nations likely to have it.

A plane is hijacked and crashed near an airbase in the UK, revealing illegal activity by the American government and sending a disillusioned Ros down a dangerous path.

Intelligence suggests an Algerian terrorist is planning an atrocity in London, so Adam returns to Ana for info on the activities of her husband, the Iranian Special Consul.

The failure of another attempt to limit the Iranian threat proves all other nations have their own agendas. Adam inadvertently kills a journalist investigating the Tehran bombing.

When Harry's plan to ground all planes leaks, Adam and Ros go undercover to prevent a nuclear warhead circuit board reaching Iran. Meanwhile, London's water supply is poisoned.

Terrorists hijack a live TV broadcast that should have heralded the signing of a new peace agreement with Iran, and Malcolm must try to disable the signal.

Ros's membership of Yalta is revealed after the organisation informs her of its plan to overthrow the American government, and working for both sides becomes her only option.

The team is suspended after Ros's betrayal, leaving the agents in the line of fire for a disgruntled former IRA terrorist about to detonate a bomb in the heart of London.

The CIA plans to assassinate the Venezuelan president in Britain in the hope of gaining information about an expected al-Qaeda attack on a school.