Series 5 begins with Britain left reeling after a series of terrorist attacks. Our team believe the attacks cloak a conspiracy to destroy democracy and turn Britain into a 'police state'. Can the team protect the democratic way of life? Zafar goes undercover and infiltrates a home-grown Islamic terror group who are planning a massive attack against London. There could also be serious repercussions for Ruth when she finds out the deaths of seven terrorist suspects in a prison fire were in fact staged by British military intelligence.

Season 4 Episode 6 - The Innocent

MI5 suspect a terrorist is planning an attack from his prison cell. Guest stars Jimi Mistry. Air Date : 13th-Oct-2005

Season 4 Episode 1 - The Special (1)

When a devastating bomb explodes in central London, causing multiple deaths, a terrorist group with a hatred for human life claim responsibility. With their leader facing extradition, the bombers announce that crippling attacks will be launched at ten hour intervals until he is released. Air Date : 12th-Sep-2005  Read More

Season 4 Episode 2 - The Special (2)

Zafar and Adam race against the clock to uncover the latest bomb. As a new ultimatum is issued and Tash mysteriously disapears, the team is forced to deal with the possibility of a mole within their own organisation. Air Date : 13th-Sep-2005  Read More

Season 4 Episode 3 - Divided They Fall

Far-right political party The British Way is threatening democracy so Adam and Fiona go undercover to infiltrate and destroy its campaign. Air Date : 22nd-Sep-2005  Read More

Season 4 Episode 4 - Road Trip

Adam infiltrates a truck carrying illegal immigrants across Europe in order to stop a would-be terrorist. Air Date : 29th-Sep-2005  Read More

Season 4 Episode 5 - The Book

A neo-conservative group murder an ex-minister to cover up his past and then they hunt down the journalist who is threatening to blow the story and is under MI5 protection. Air Date : 6th-Oct-2005  Read More

Season 4 Episode 6 - The Innocent

MI5 suspect a terrorist is planning an attack from his prison cell. Guest stars Jimi Mistry. Air Date : 13th-Oct-2005  Read More

Season 4 Episode 7 - Syria

The Syrian foreign minister tries to establish subversive contacts with MI5 at the opening of a cultural centre in London. Fiona is desperate to lead this mission and must confront her Syrian past. Air Date : 20th-Oct-2005  Read More

Season 4 Episode 8 - The Russian

An old British traitor is called in to infiltrate a Russian firm suspected of stealing secrets from GCHQ. Air Date : 27th-Oct-2005  Read More

Season 4 Episode 9 - The Sting

Harry upsets the CIA by stopping an extradition to the USA. Air Date : 3rd-Nov-2005  Read More

Season 4 Episode 10 - Diana

A former officer is convinced that MI5 killed Princess Diana and is determined to force the team to prove it. Air Date : 10th-Nov-2005  Read More