A GROUP of holidaymakers in Cairns, Queensland, leave their four boisterous young boys together in one of their hotel rooms while they have dinner downstairs in Candice Fox’s Gone By Midnight (Century, £12.99).

Every hour one of the parents checks the room, and all is well until midnight on the second evening, when the hourly check reveals only three children.

Evidence from CCTV suggests that the missing Richie can’t have left the hotel and tracker dogs find no trace of him within it. How can he just have vanished?

Fox poses an intriguing puzzle, neatly resolved by two of the most unusual private detectives around — most in fiction argue with the police but the cops literally want these two dead.

Since 1969, Michael Z Lewin has been writing books about Indianapolis private eye Albert Samson, who lives over his mom’s luncheonette and has never owned a gun. Among aficionados, they are considered some of the best and most distinctive work ever to appear in the gumshoe genre.

Alien Quartet (iUniverse, £11.95) is a set of four linked short stories, in each of which Albert has the same eccentric client — a young man who believes that his absent father was an extraterrestrial.

The only superpower he’s inherited, he says, is an ability to empathise, though to Samson it seems more like an inability not to emphasise, no matter how inappropriately. All of which means plenty of trouble for the soft-boiled detective who has his own paternal problems to resolve.

Elizabeth Mundy’s A Clean Canvas (Constable, £8.99) is the second outing for Lena, a Hungarian cleaner living in north London. This time she’s forced to investigate the theft of a painting from the Islington gallery she’s working at, when her unreliable cousin vanishes immediately after the robbery.

The only way to prove the girl’s innocence is to find the real culprit among the inhabitants of the weird world of art collectors, using the detective skills she’s learned from her domestic work.

Witty and warm but with an unsentimental core of steel in its chronicling of London’s guest-workers, this looks set to become a highly popular series.

In 1950s Finland, the shortage of men is so severe that the police have been forced, with undisguised distaste, to employ a female detective.

It’s well-known that women are too emotional for serious casework, which is why Sergeant Hella Mauzer is based in quiet Lapland in Evil Things by Katja Ivar (Bitter Lemon Press, £8.99).

When she’s sent to deal with the seemingly routine disappearance of an old man from a village cut off from the rest of the world by snow, no-one expects her to uncover, let alone solve, a crime.

But Mauzer will need all the stubbornness her bosses accuse her of when she realises that something more awful than mere murder has taken place. Cold-war Lapland is a glitteringly fresh setting and the protagonist is an unexpected character who I’d love to meet again.