A NORTHUMBERLAND gang boss comes out of prison a changed man, in The Dark Heart by Neil Lancaster (HQ, £16.99). Unfortunately, it’s not a change for the better: he’s been radicalised by a white supremacist mentor, and from now on all his energies are devoted to a cause greater than simply getting rich.The resulting sequence of gruesome murders alerts Max Craigie and his Police Scotland anti-corruption team to a frightening conspiracy. If they can’t uncover the mole in law enforcement quickly, Britain could be sent tumbling into a race war.