Straw Dog (2)

Someone is harassing Grace Foley about her old testimony against Tony Greene. The demand: admit she was wrong, or the hostage dies. Straw Dog (2) puts its quietest character at the centre of a screaming clock, and Sue Johnston plays it without a wasted gesture.

The team works two directions at once. Backwards, into Grace's past and what her evidence actually rested on; forwards, through interrogation sessions with a desperate drug addict who once snatched her purse. That thief turns out to matter more than he should, because between him and a lovesick ex-con willing to help, Boyd and the squad start closing on whoever is holding and torturing a young man right now. Whether this is Greene himself or someone copying his old crimes stays live until late.

Declan Croghan and Barbara Machin wrote it, Jim O'Hanlon directed. Trevor Eve is Boyd, Wil Johnson is Spencer Jordan, Esther Hall plays Dr Felix Gibson and Félicité Du Jeu is DC Stella Goodman. Emma Lowndes appears as the younger Grace in flashback, which gives Johnston's performance something to argue with. Tom Ellis is Harry Taylor, Paul Freeman is Dr Charles Hoyle, Terence Hillyer plays Terry Healey and Eugene O'Hare is Kevin Keogh.

The episode's real subject is what testimony costs. Grace said what she believed years ago, professionally and honestly, and now a stranger wants her to unsay it with a gun to someone else's head. Standing firm could kill an innocent person. Recanting would be a lie.

That is a genuinely cruel dilemma, and the episode earns the tension rather than borrowing it from a twist. Grace is a profiler whose whole working life rests on reading people correctly; being told to declare herself wrong is an attack on more than her pride.

The flashback material with Emma Lowndes helps. Seeing young Grace make the choices she is now being tortured for gives the pressure a history, and Johnston plays the older woman as someone re-reading her own past under duress.