Episode 7

A French scientist has gone renegade with a top-secret weapon called Firestorm, and he's shopping it to the highest bidder from British soil. That alone would be enough for a busy week. Then the French turn up wanting to work with MI5, and the real game begins: the British want the technology for themselves, which means stealing it back without the French finding out, using an agent who, if caught, belongs to nobody. Firestorm is the sort of codename the show delivered deadpan, and the weapon itself is never quite the point. The game is about who ends up with the weapon and who gets blamed for losing it.

The burglary at Harry's flat puts the whole operation in doubt, or seems to. A burgled flat in a spy show is never just a burgled flat. The episode enjoys that ambiguity, letting the audience wonder if Harry is compromised or playing a game of his own. It's classic Spooks territory, and the hour handles it with the show's usual economy.

Simon Mirren and David Wolstencroft wrote it, Ciaran Donnelly directed. Matthew Macfadyen's Tom and Philippe Caroit's Jean-Luc square off across the Anglo-French divide, Megan Dodds's Christine and Keeley Hawes's Zoe keep the home end busy, and Peter Firth's Harry does what Harry does best: hold back more than he reveals. Philippe De Grossouvre's Bertrand, Geoff Cotton's Durand and Shauna Macdonald's Sam Buxton round out the cast, with Adam Deacon's Billy among the younger faces on the street.

The Firestorm plot is solid. But the real subject is trust between allies, and the burglary turns it personal. Whatever the answer to the mystery at Harry's flat turns out to be, the episode knows that the question was always the point. And the hour plays fair with the viewer, which is the least and the most a spy story can do.