Silent Witness, series 15, episode 1, review "Perhaps we're not meant to do this job for ever," said Nikki (Emilia Fox) to Harry (Tom Ward) in Sunday's Silent Witness. BBC One, though, doesn't seem to agree - given that this was the 65th episode in which Fox was required to look pensive in white overalls, and the 85th in which Ward got to deliver little homilies about the importance of forensic pathology. As for the programme itself, it remains a reliable mix of the intriguing and the plain bonkers. Certainly, the opening scenes were pretty much as we've come to expect - which is to say that we didn't have a clue what was going on. A grizzled detective stared at the photofit of a sinister-looking woman. A sinister-looking woman stared at the camera. One pathologist was stabbed at a crime scene. Another slit her wrists. Meanwhile, a hooded figure approached a shop with a woman's voice urging him to "Do it." And all the time, Nikki was declaiming Dylan Thomas's And Death Shall Have No Dominion. It took a while for these strands to come together, but by the time they did, Silent Witness was firmly on the intriguing side of the mix. Among other things, the hunt was now on for "The Wraith": a female serial killer whose DNA had been found at murder scenes for 12 years. She'd been identified by the psychological profiler as "a sociopathic narcissist who lives for kicks and likes taunting the police" - or, as it's known to longstanding viewers of crime dramas, "the usual." Leading the hunt was Tom Byrne (Vincent Regan), that grizzled detective of the opening scenes, who despite possessing all the traditional signifiers of an old-school copper (loosened tie, stubble, whisky bottle in his top drawer, being Scottish) proved unexpectedly sensitive. Even so, the Wraith had become to him roughly what Moby-Dick was to Captain Ahab. But then in Monday's concluding episode, the bonkers side came roaring back. The murders, we learned, hadn't been committed by the Wraith at all - largely because, despite that photofit, she didn't exist. Instead, the DNA had been planted by a pathologist with a grudge against Byrne. As an inevitable result, he'd kept a dead junkie on hand for the past 12 years, raiding her corpse every time he wanted to plant more. Yet the real mystery here is that once again the show just about got away with it. The main reason, I think, is the eerily calm way the actors go about their business - for all the world as if they're in a perfectly normal and believable crime drama. In Silent Witness, as in farce, the key is to play it absolutely straight.