The Janus Stone, By Elly Griffiths

Funny it's so difficult to find a doctor on call when pathologists seem to be queuing up to sort you out once you're dead. Here comes another one, but Ruth Galloway, expert in Roman remains, is a special creation. She isn't a sexless zombie in a starched white coat; she is really, messily, female. And she doesn't always get things right: her pregnancy is a big surprise. It's even more of a surprise to her puritanical parents.

Ruth and her lover, DCI Nelson, are believable beings at the centre of Elly Griffiths's archaeological mystery. Her pregnancy adds to the intensity of her feelings when the skeleton of a child is discovered under the doorway of an old house: a burial that might have been common in antiquity, when entrances were under the guardianship of the two-headed god, Janus, and the even more fearsome Hecate, to whom such sacrifices were made.

But this infanticide could have occurred nearer modern times, when the building was occupied by a children's home. Two small inhabitants were reported to have run away, leading to suspicions about the charismatic local priest in charge. Ruth lends her expertise to the search for the missing children, and finds a potential murderer amid a heady brew of classical lore and psychopathic revelations. The Iron Age excavation on which she is working is run by an archaeological prima donna (authentically depicted). Also hanging around the trenches are the former lord of the manor and a New Age spiritual adviser who turns out to be remarkably practical beneath his encumbrances of cloak and necklaces.

The setting is enticingly atmospheric: very flat, Norfolk may be, but it also has mysterious fogs and waterways that lead to a gripping chase, excellently interwoven with the Latin quotations and carbon-dating. Meantime, Ruth and her DCI face the big decisions: will she continue with her pregnancy, will he tell his wife? I closed the book wanting to know more about them as well as feeling the satisfaction that a really intelligent murder story can give.