Subterraneans (2)

The cellar gives up another body. This is the same cellar where the missing businessman spent his captive year, and what's found in it now is a man murdered brutally enough to make the first death look gentle. The cement factory killings and the imprisonment are no longer separate threads; they're one story with a very damp floor.

Boyd's team settles on Dr Nick Henderson as the man behind the two factory murders, and here's the episode's real engine: they're convinced, but conviction isn't proof. Everything the team does in this hour is the unglamorous work of turning certainty into evidence a court will accept. Suspects who look unlikely get pulled in, connections get established, and the gap between knowing and showing turns out to be where this whole case lives. It's honest about that. Most crime dramas pretend the hard part is finding the killer; Waking the Dead has always known it's pinning him down.

Barbara Machin and Ed Whitmore wrote it, Michael Offer directed, shown the night after part one in October 2005. Trevor Eve leads as Det Supt Peter Boyd, with Sue Johnston as Dr Grace Foley, Wil Johnson as DI Spencer Jordan, Esther Hall as Dr Felix Gibson and Félicité Du Jeu as DC Stella Goodman. Toby Stephens plays Dr Nick Henderson, with Nicola Stephenson as Julia Henderson, Ronan Vibert as Dr Jonathan Lynch, Ayesha Dharker as Mary Sharman and John Bennett as Professor Rosenthal.

The pairing of Boyd and Henderson is the hour's best asset. Toby Stephens plays him polished and reasonable, which is precisely what makes him unnerving; every interview scene feels like two men fencing politely over a corpse. And Grace Foley gets the material that asks what a year in a cellar actually does to the person who survives it.

Methodical is the right word for this half, meant as praise. The mystery comes apart piece by piece, and the pieces are ugly.