Just when you think the police murder procedural has nowhere left to go, up pops a drama such as Whitechapel that nudges the genre a little further, courtesy of beautifully imagined and portrayed offbeat characters and quirkily atmospheric storylines.
At the helm of the strange little investigation team is DI Chandler, played by Rupert Penry-Jones with an almost Sherlockian air of obsession. His Doctor Watson is the dishevelled and cynical DS Miles (Phil Davis).
Together they hunt killers through the streets of London's Whitechapel, each of whom appears to have taken their cues from grisly murders of years gone by. Admittedly, this last point does require a substantial suspension of disbelief - one well-read psychopath is plausible but a whole swag of history-obsessed maniacs is a little hard to swallow - but once you accept this and come on board, the ride is great fun.
This episode is the second of a two-parter that began with bits of victims turning up around the team's patch like so many badly made Barbie dolls. The killer, it appears, has refined his technique based on the adventures of the Marquis de Sade, which sends Chandler, Miles and the others off into some dark place indeed. Proceedings are also enlivened by the characters' banter. "If only we knew what the corpse looked like," Miles says. "Well," replies the pathologist gravely, looking over a table of body parts, "only the head can tell us that."