Episode 5

It opens on a Saturday morning, which in Spooks means the personal lives get a look in before the work starts. Danny and Colin are on the gun range, keeping their aim honest. The range is the only place where the rules are simple. Zoe and her fiancé Will are still in the dizzy stage of an engagement. Ruth is at home with old films, wishing her own life had a little of that romance in it.

Then the trail of a rogue scientist gets in the way of the weekend. The scientist is the kind of target that never stays put, and the mission, which eventually ends up in the North Sea, puts strain on every relationship it touches. And Zoe catches the blame: she is accused of letting her feelings for Will interfere with the job, the kind of accusation that sticks no matter how well you work. Zoe has to keep working while it follows her around the office. Barnaby Kay's John Fortescue and Dermot Crowley's Eric Newland are the faces of the operation. Debra Gillett appears as a psychologist, called in to give the suspicion official weight. There is even a waiter, played by Luke de Lacey, because somebody has to pour the wine while careers are decided.

Peter Firth's Harry, Richard Harrington's Will, Keeley Hawes's Zoe, Shauna Macdonald's Sam, Rory MacGregor's Colin and David Oyelowo's Danny make up the ensemble. It's an episode built on small moments between big ones. David Wolstencroft wrote it; Justin Chadwick directed.

The hour balances the operational work with the emotional fallout, and the reminder lands: in this line of work, attachments are a vulnerability. But knowing that doesn't make it easier to live with, and the episode is honest about it. Ruth's old films feel like the truest note in the whole piece. The ending doesn't resolve the relationship question, which feels right for a show that never lets its people settle.