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.

For gritty police procedurals with a recurring cast of endearing and at times eccentric characters, this is one of the best series around. If only it weren’t all a fantasy, and we really lived in a country where cops and spooks concentrate on violent fascists rather than peaceful dissidents.

Nell works for a London charity and lives as quiet and self-denying a life as she can, haunted by a terrible guilt, in When I Kill You by BA Paris (HQ, £16.99). Years earlier, as the only witness to a violent crime, she took matters into her own hands. But she got it disastrously wrong.

And now, she’s convinced that someone is following her. Is it the man who swore, as he was led from court to a prison sentence, that one day he would kill her? Or is something even more sinister going on?

An expertly paced suspenser, this is a proper “keep-you-awake-all-night” novel.

Edinburgh heart surgeon Matthew is more than happy to answer a summons to jury service, in Witch Trial by Harriet Tyce (Wildfire, £18.99). It’ll give him an opportunity to hide from his problems at work and home. But the case to which he’s assigned is horrific: two schoolgirls, obsessed with witchcraft, are accused of murdering a friend.

The evidence burns into Matthew’s consciousness and his dreams alike, and some of the dreams come while he’s still awake. It becomes clear to the reader that he’s suffering a major breakdown. But through it all he remains convinced of one thing: there is something fundamentally wrong with the prosecution’s case.

There aren’t nearly enough novels set in the unique Scottish legal system. Let’s hope this riveting combination of psychological and courtroom drama starts a new trend.

If you can get a place at Ravensthorpe you’re more or less guaranteed a successful literary career — it’s the UK’s premier degree-level writing course. But Tess, narrator of The Pact by Lisa Walker (HQ, £9.99), struggles to fit in; too working-class, not ruthless enough. In the end though it’s a tragic death that causes her to drop out of the college.

Three years later a reunion of sorts takes place, walking the Camino de Santiago, Spain’s famous pilgrim route. To everyone’s surprise, Tess turns up. She has revenge on her mind — but she’ll have to be quick, because she’s not the only one.

Written with an effervescent, irreverent humour, this mystery thriller is also rich in twists and shocks.