Birdhouse

Vickers and Kirsty are off on a Home Office jaunt, which is the show's way of saying Joe Robinson gets to run the squad for a week. His target is a club owner, thoroughly reviled, suspected of turning a profit from the drug dealing on his own premises. It looks like a straightforward job. Then the club turns out to be a base for human trafficking, and the straightforward job becomes something else entirely. The drugs were only the surface of it.

The episode has a quiet joke at its centre. Adam Parkes' irrepressible sexual urges are supposed to be the key that unlocks the case, and they get him exactly nowhere useful. But it is Stuart Cole, the family-values sergeant, who delivers the essential witness and seals the club owner's fate. The show has always liked surprising you with who does the dirty work, and the reversal lands anyway.

Jake Nightingale's Cole gets a rare turn in the spotlight and makes the most of it, and Mel Raido's Parkes wears his own failure lightly. The club owner himself stays a silhouette of menace, which is all the role needs. Katrine De Candole's Roberta and Agnieszka Liggett's Alexa are the women the trafficking was built around, and the episode keeps them in frame rather than hiding them. There is no glamour in the way the show films any of it, which is the right call.

Around the case, Hutchins and Johnstone do the grinding work, and Robinson steers the whole thing without Vickers to answer to, which suits him. Frank Grimes' Peter Avery rounds out the supporting cast.

Shan Khan wrote it, Jon East directed. It is an efficient, sour hour that starts as a drugs case and turns into something much darker, and the title suits it. A birdhouse is a place where things are kept, and nobody in it sings for joy.