Episode 2

Calum Reed gets mugged. That is the whole engine of this episode, and it should not be enough to power an hour of television, yet it nearly is. He is taking part in a routine intelligence-sharing exercise with MI6 when a gang of street muggers sets on him and lifts his laptop. On that laptop: the names of MI5's undercover assets, every one of them. The sort of information that is supposed to stay in a locked room. Ordinary muggers, ordinary bad luck, and a catastrophe.

The names are on the internet before anyone can blink, and the damage is immediate and public. MI5 looks incompetent, which is bad for the service and worse for the people whose lives are now hanging in plain sight. The episode spends its hour on the fallout: protecting the deepest sources while the whole world scrolls past their names. Every agent with a face on the internet is a target now, and every handler with a phone starts counting the cost. It is a story about information, which means it is a story about how quickly trust dies.

The cast is the usual reliable set, and the episode leans on them rather than on stunts. Peter Firth's Harry, Nicola Walker's Ruth, Max Brown's Dimitri, Lara Pulver's Erin and Geoffrey Streatfeild's Calum carry it, with Shazad Latif's Tariq, Tom Weston-Jones's Sasha, Alice Krige's Elena, Jonathan Hyde's Ilya and Simon Russell Beale's William Towers in support. Geoffrey Streatfeild's Calum carries the guilt of it well. Jonathan Brackley and Sam Vincent wrote it, Alrick Riley directed.

The mugging itself is almost mundane, which is the point. The service runs on ordinary people doing careful things, and one careless afternoon undoes years of it. But the quietest moment is watching seasoned officers realise their own secrets are no longer theirs. That lands harder than any explosion.