Apparitions, 13 Nov, BBC One

With the knives currently out for the BBC, this - the first episode of a supernatural six-parter by Joe Ahearne (This Life, Ultraviolet, Doctor Who) - is a gutsy, skilfully crafted and highly enjoyable piece of work.

It focuses on the inner doings of the Catholic Church - particularly Father Jacob (Martin Shaw), who works for the office that investigates candidates for sainthood. However, he is also a skilled exorcist - and is being touted by the current Chief Exorcist as a possible successor.

Back in London, a little girl appears at the seminary where Fr Jacob is based, claiming that her dad is possessed. What follows is a tense game of cat and mouse between the priest and the father (Shaun Dooley), who may be possessed or may just be a particularly ardent atheist.

There's some absolutely excellent writing by Ahearne, who also directed the episode, as the two men engage in a verbal game of chess, each shielding their real agenda behind a mask of civility and thinking several moves ahead to gain an advantage. Some of the scenes reminded me of the gripping interviews between Frank Longford (Jim Broadbent) and the chillingly devious Ian Brady (Andy Serkis) in Peter Morgan's Longford.

In form, the series resembles a cop show. Fr Jacob, the capable and resourceful officer, faces hostility and interference from his superior (John Shrapnel). He employs Colombo-style stealth as he looks for clues and gathers evidence to shed light on the father's 'possession', before Shrappers in effect demands his gun and badge and takes him off the case.

Almost from the start, the series is in no doubt about the existence of demons and dark forces, although it's all done on a very domestic level, with a refreshing lack of grand guignol. In fact, the only bit of gore, very near the end, seems totally out of tone with the suspense and atmosphere of the rest of the ep, though it has been subtly set up throughout. The whole thing is cliche-free and relevant; in this world, demons have very human faces.

Shaw is note-perfect as the magisterial priest, and the episode creates a great deal of anticipation about the impending 'war', in which Fr Jacob is going to be a key player. This is classy stuff - I bet the beautifully lit interiors and cityscapes of Rome look amazing on HD. The best first episode I've seen on the Beeb for yonks.