Another very twisty spy story, again featuring Basil Dignam as the incredibly untrustworthy head of MI5. This time, the trail of a man played by guest star Robert Urquhart who bailed out of an airplane over the English Channel and started a brand new life that he set up for himself many years before turns up evidence that he’s a double agent. Department S learns he’s a double agent, the narrative shows he’s a double agent, there are three Russians looking for him, so why doesn’t MI5 believe that he’s a double agent?
Unlike Smith’s previous appearance, this is a very kid-friendly story, with nothing in the episode that’s too weird or underplayed. Plus, there’s a great little car chase where Annabelle is being followed by one of the Soviet agents through central London and loses him very imaginatively. Later on, she gets the predictable “you stay here” from Stewart, but she acquits herself really well in that scene, I thought.