Tom and Helen must go undercover and befriend the wife of a suspected hardcore racist in order to prevent a racewar. Meanwhile Zoe and Tessa learn that a boatload of refugees is due to dock at Dover in the next few days. Things worsen when the operatives realise the two things may be connected and their covers may be blown.

Disgraced MP Hampton Wilder has written memoirs with the power to destroy the government, what's more an old KGB agent is trying to smuggle illegal arms into and out of the country, besmirching the good name of the Prime Minister's right hand man.

Tom is undercover with Customs, but when he goes off to phone in, the rest of the crew are murdered. A Colombian drugs cartel are suspected. Zoe and Tom are sent undercover to 'turn' the girlfriend of the head of the cartel. Tonight also sees the re-appearance of Tessa and she wants revenge on Harry and MI5. Will she endanger Tom and Zoe's life? Will the mole be found before it's too late? Or will Tessa get her revenge and allow someone to die?

Tom ignores Harry's demands to end his relationship with CIA officer Christine Dale. Christine hands Tom a secure communication which she has accidentally received from high up in the CIA. It says that an American assassin has come to the UK for a hit and that the CIA are going to take him out, without informing Five or any of the security services. Tom can't tell Harry what he knows so enlists Danny and Zoe to help him. However, things start to go wrong and tonight's episode is all 'Smoke and Mirrors'. Will the truth be uncovered before something goes terribly wrong? Has Tom gone bad?