Spy Game

On advice from the CIA, Palfrey puts an American aerospace engineer under surveillance. The man is suspected of passing classified information about an Anglo-American defence project to the Soviets, and the case looks as though it may unearth the mole. There is a catch the size of the Atlantic: can Palfrey trust the CIA, or is he being pointed at someone the Agency would rather see gone? Meanwhile, the episode carries a second thread, the murder of a fellow spy, and the roots of that death turn out to lie in a battle fought centuries ago, far older than the Cold War that surrounds it.

Barry Appleton wrote the episode and Gerald Blake directed it, and the two strands, the modern and the ancient, sit together more easily than they should. The historical thread gives the hour its odd, appealing depth; the surveillance plot gives it its pace. It is a good example of the second series at its most assured, willing to hold two very different stories in the air at once. Nothing here is shouted, and the quiet is the point.

Alec McCowen anchors it as Palfrey, with Caroline Blakiston as the Coordinator, Clive Wood as Blair, Briony McRoberts as Caroline, Dallas Adams as Roche, David Baxt as Madison, Andrew Bicknell as Thruxton, Dennis Edwards as Mr Turnbull, Andrew Blair as the Radio Operator and Peter Harding as a Special Branch Officer. The small parts do their job without fuss, which is the mark of a cast that trusts the writing.

It is a reminder that the deepest secrets are rarely contemporary ones. They are layered, like old walls, and the freshest coat of paint hides the oldest cracks. And for all the modern surveillance and the Anglo-American politeness, the case comes down to old grudges, which is where this show always liked to find its truth.