Harry faces deportation by the CIA - but when Elena reveals information about an imminent attack on the UK, his colleagues decide to break him out of custody. [S]
Harry kidnaps CIA deputy-director Jim Coaver and interrogates him about the recent attacks on MI5, but he soon realises his former Cold War colleague could be innocent. [S]
An imprisoned religious extremist leader sends two men on a suicide bombing mission, unaware one of them is an MI5 spy. Meanwhile, an attempt is made on Elena's life. [S]
Dimitri gets close to the sister of a dangerous anarchist in a bid to discover where he is hiding, while Ruth considers an offer to become the Home Secretary's security adviser. [S]
Calum is attacked by muggers who take his laptop containing classified information on MI5's undercover agents, leading to a race against time to save the spies from being exposed. [S]
Ruth is drawn into a dangerous situation involving the death of a Mafia leader, and Lucas has a confrontation with Harry destined to change Section D for ever. [S]
A White House representative visits the UK to install an American security system, unaware it will allow foreign hackers to access all of MI5 and the CIA's information. [S]
Lucas tracks a Somali terrorist on a ship destined for Plymouth, but when it emerges the vessel is carrying an explosive payload, the team races to prevent a disaster. [S]
The Nightingale group plans to kill Pakistan's president at talks designed to stop the conflict between his country and India escalating into nuclear war. [S]
A double agent reveals plans to incite conflict between Hindus and Muslims on British soil, but his handler is working with Caulfield, who will go to any lengths to silence him. [S]
An informant who could allow an almost bankrupt British government access to £1billion refuses to share vital data - and a group of assassins is looking for him as intently as Ros. [S]
The Mole: Harry is arrested after being framed as the mole who revealed classified information. With Britain under renewed threat of nuclear attack, the whole team comes under suspicion. [S]
A Chance for Peace: Harry and Ros agree to meet an al-Qaeda terrorist leader, who is offering to exchange intelligence on a planned bombing in London for the pardoning of two prisoners. [S]
Split Loyalties: Harry vows revenge on Kachimov following the explosion, but the government demands proof of Russian involvement. Lucas is desperate to return to the Grid. [S]
Infiltration: 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. [S]
The Broadcast: 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. [S]
The Courier: 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. [S]
The Deal: 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. [S]
The Extremist: 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. [S]
The Kidnap: 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. [S]
The Virus: Part 2: 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. [S]
The Virus: Part 1: 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. [S]
Aftermath: Adam and Ros try to negotiate with a group of environmental terrorists threatening to flood London unless the Government release a secret document. [S]
The Criminal: Adam is approached by his treacherous former partner, who asks for his help when the team are assigned to protect a high-profile witness. [S]
Agenda: The team is given cause for concern when a Muslim cleric is killed by an assassin apparently fighting in the name of extremist Christianity. [S]
Hostage Takers - Part Two: The terrorists demand the release of al-Qaeda prisoners in Saudi Arabia and resort to killing the hostages when the government refuses to negotiate. [S]
Hostage Takers - Part One: Adam and Zaf track down an elite team of terrorists that has entered Britain, while Ros safeguards a group of Saudi princes. [S]
The Message: Harry suspects foul play when a group of terror suspects are killed in an alleged accidental prison fire, but fails to act and a member of his team is framed for their murder. [S]
The Cell: Zaf goes undercover to infiltrate an al-Qaeda cell planning a bomb attack, while Adam tries to stop the terrorists reaching their target. [S]
Gas and Oil - Part Two: Harry races to prevent Britain being turned into a dictatorship as the conspirators exert their control over the Prime Minister, but is taken prisoner. [S]
Gas and Oil - Part One: Adam returns to work when multiple terrorist attacks plunge Britain into chaos - and it seems there could be an enemy within. [S]
Diana: A former spy holds the team hostage, demanding its members produce evidence that the security services assassinated Diana, Princess of Wales. [S]
The Russian: The agents rely on a well-known traitor as they infiltrate a Russian company, but Adam's state of mind could prove just as dangerous to the operation. [S]
Syria: Fiona defies Adam's wishes and goes undercover to handle security at a conference. She discovers her ex-husband is also attending - and planning to exact revenge for the past. [S]
The Innocent: The agents organise the release of an imprisoned terrorist they suspect of planning an attack from his cell, but find their assumptions challenged as they track his movements. [S]
The Book: The team protects a journalist about to break the story of a former Cabinet minister with a shady past who was murdered by a neo-conservative group.. [S]
Road Trip: Adam and Zafar travel to Turkey to persuade an Islamic terrorist to defect - but the team is uncertain whether its new recruit is all he seems. [S]
The Special (Part 2): Zafar and Adam race against the clock to uncover the latest bomb, and the team begins to suspect there is a mole within their organisation. [S]
Celebrity: Third series of the popular, edge-of-the-seat spy drama. MI5 investigate the abduction of a famous couple's child. There's more to the kidnapping than at first appears. [S]
Outsiders: Rupert Penry-Jones stars in the thrilling drama about the modern security service. Ruth investigates some computer hackers who may be linked to Islamic terrorism. [S]
Who Guards the Guards?: Another nerve-shredding episode of the slick spy drama. Danny and the team must investigate an assassination attempt on a famous novelist. [S]
Sleeper: Another edge-of-the-seat episode of the classy spy drama. Harry reawakens sleeper agent Fred Roberts, a renowned family man, and Tom suffers a crisis of conscience. [S]
Project Friendly Fire: More nail-biting drama from the slick spies. The team must prove the innocence of missing colleague Tom and save the service from government takeover. [S]
Christine: Keeley Hawes stars in the super-suspenseful action drama about the UK's Security Service. Danny and Zoe are forced to spy on Tom as a US assassin is dispatched to Britain. [S]
Drugs: Keeley Hawes stars in the tense drama series about the British Security Service. MI5 come up against oil corruption and the Chala Cartel, Colombia's biggest drug traffickers. [S]