'Ice Moon' by Jan Costin Wagner

Fiction - paperback; Vintage; 288  pages; 2006. Translated from the German by John Brownjohn.

A serial killer who smothers his victims while they lie sleeping is on the loose in Turku, Finland. He leaves few, if any clues.

Young CID detective Kimmo Joentaa is put in charge of the investigation even though, by rights, he should be on compassionate leave: his wife has just died of a terminal illness.

Joentaa throws himself into his work as a means of distracting himself from his own grief. But at each murder scene, the dead bodies remind him of his dead wife. Over time, he begins to develop an affinity for the murderer, because he seems to take great care in ensuring that his victims do not suffer and that is how Joentaa wanted his wife to be treated in her last, dying moments.

But the killer is far from humane. A seemingly invisible and quiet man, he has a personality disorder kept hidden from his own family and work colleagues. "What would you say if I was completely different from the way you think I am?" he asks his brother one day. "If you were different, I would be very sad," comes the almost prophetic response...