A Different Type of Threat (Part 1) : Season 22 Episode 57

Fletcher is hand picked by officers from Special Branch to infiltrate the "Racial Defence Army", a local left-wing group whom Special Branch suspect are about to carry out a major-scale attack on London. Posing as a racist police officer, Fletcher asks his friend Ewan, already a member of the group, to arrange a meeting with group leader Robert Barry. Fletcher is initially welcomed into the fold, until another member of the group, Nick, becomes suspicious when the group's plan to kidnap a radical Muslim cleric goes wrong. Nick then carries out a kidnapping of his own - but when his plans are once again thwarted, Nick confronts Fletcher and discovers that he is working undercover.