Black magic in London: Crimes of passion The Boy in the River. By Richard Hoskins. Pan Macmillan; 334 pages; £7.99. IN THE late 1980s Richard Hoskins, young and newly married, spent six years as a missionary in Bolobo, upriver from the Congolese capital, Kinshasa. Now back in Britain and something of an Africa specialist, he advises the authorities on tribal and ritual crimes. In his new book, "The Boy in the River," Mr Hoskins argues that these atrocities are a perversion of African belief systems and highly unusual. His first case, in 2002, involved the mutilated torso of a boy they named Adam, found in the River Thames. The police thought it was a muti killing, a South African practice that involves removing organs for use in tribal medicines. Mr Hoskins recognised that Adam was in fact a human sacrifice (a term the police initially recoiled at) by a Nigerian tribe. His evidence was the precise slit in the victim's neck and a body drained of blood - a divine tribute that is condemned as juju, or black magic, in West Africa. The boy's killer has not yet been convicted, but the investigation did uncover a trafficking ring that smuggled African children to Britain for such ritualistic abuses. Mr Hoskins and his wife suffered their own tragedy in Congo; one of their twins was stillborn, the other died before she was two. He admits his work presents emotional challenges. But he is not overly sentimental. He writes about criminology, how the police deal with the media and the perverted beliefs behind the crimes. Much of the book is about kindoki. Mr Hoskins understands this as a benign affliction treated with a potion of plant extracts from a nganga, a traditional healer. But there is a growing trend of pastors in new revivalist Christian churches, both in Africa and Britain, preaching a different, malevolent kind of kindoki. They convince parents that their children are possessed by demons which must be exorcised through isolation, fasting and beatings. Gullible and desperate believers, who consider their pastors to be "little Gods," will pay good money for them to cure this malady. The most harrowing case is that of Kristy Bamu. Attempting to exorcise the boy of kindoki, his sister and her boyfriend tortured him to death over five days in December 2010 using an array of weapons, including light bulbs, floor tiles, knives and pliers. Mr Hoskins testified in court that Africans do not practise exorcism like this. It is heartening to read that the British authorities go to great lengths to solve these crimes, but infuriating to learn about the flaws in the system. An important witness to the Adam crime, for example, was deported before she could be properly questioned. An eye-opening book that makes a strong case for cultural understanding.