|Series 01, Episode 04|
|Air Date||4 June 2002|
|Previous||One Last Dance|
|Next||The Rose Bed Memoirs|
Danny and Zoe recognise Peter Salter (guest star Anthony Head), a senior MI5 agent and Tom's mentor taking part in an undercover operation during an anti-Bush rally, in order to stop a terrorist group. However, it is revealed that Salter has switched allegiances to the terrorists after he has fallen in love with one of the members, Andrea. They break into a university campus to tamper with an Air Traffic Control system to take down the President's plane coming to visit the UK. Salter is captured, but the group escape. Rather than give them away, Salter commits suicide. Meanwhile, Ellie discovers her boyfriend is a spy. Zoe learns that Tessa is corrupt by setting up false agents for money.
After getting shot during the Turkish consulate raid in the previous episode,Tom Quinn is on sick leave until he recovers. When Ellie notices Tom's wound, he is forced to reveal he is a spy. Over the course of the episode, Ellie threatens to leave Tom unless he confesses to her daughter, Maisie (Heather Cave). After eventually doing so, Ellie starts to accept him.
Danny and Zoe observe an anti-globalisation rally before Bush's visit, where a riot ensues led by a man in a flaming helmet, who spots the two and flees with a young woman, Andrea Chambers. When they are surrounded by riot police, the man reveals himself as Peter Salter, a legendary MI5 officer who recruited Tom. They contact Tom after they weren't briefed about the situation. Harry Pearce admits that Salter is working with Harry and Jools Siviter at MI6 in a joint operation to take down a European anarchist terror group led by Istvan Vogel. In order to get into the cell, Salter has been sleeping with Andrea. Upon meeting him, Tom questions Salter's allegiance after learning he is in love with Andrea; Tom reluctantly allows the operation to continue, but displays his concern to Harry.
Tom's concerns are revealed to be correct, as Salter and Andrea evade Danny and Zoe. Zoe is sent to meet up with one of Tessa's contacts, who may have information on where Salter is. However, upon waiting, Tessa arrives; Zoe works out that Tessa is running several phantom agents and pockets their money. In order to keep Zoe quiet, Tessa bribes her £10,000. Salter meets with Vogel in Wales. There, Salter offers his plan to take down the President; they break into a University researching Geographic Topology. There, Salter breaks into the database and manipulates the flightpath of Bush's plane, and the nearby topography to cause the plane to crash. By the time all but Salter leave, Armed Police arrive and arrest Salter, who is brought to Thames House.
After reluctantly telling Tom where Vogel's group are hiding, Salter hangs himself before revealing what he did in the campus. Harry learns about Danny hacking his way into improving his credit rating, and destroys his credit cards. As punishment, Danny is to train new staff. There, he learns of Salter's intentions; the plane is diverted to Paris. In the end when Ellie asks Tom about his day, he replies; "a man, who believed in a cause, killed himself for love, totally pointless."