The Uninvited Guests, By Sadie Jones

It's the spring of 1912 and Emerald Torrington is preparing to celebrate her 20th birthday. Florence the housekeeper is decorating a cake, the scullery maids are polishing the silver, and younger siblings Clovis and Smudge are off to the stable block. So far, so Downton. But as the day unfolds it becomes apparent that this peculiar tale owes more to Saki and JB Priestley than Julian Fellowes.

Sadie Jones set her first two novels, The Outcast and Small Wars, in the drab 1950s. Here she takes relish in recreating a familiar Edwardian landscape, peopled by eligible cads and imperious dowagers. The family seat, Sterne, might be an imposing edifice surrounded by black yews and creamy magnolias, but the money has long been spent. Indeed, Emerald's stepfather, Edward, is off to Manchester to try and secure a loan from "an industrialist of low morals".

What starts off as a pastiche of a country-house melodrama turns into something much more macabre. Just as the ladies have finished pouring themselves into evening gowns there comes news of a dreadful accident. A train has come off the tracks, and Sterne must accommodate the survivors. As the first party guests arrive, a group of whey-faced "third -class" passengers can be spotted picking their way across the fields.

Bringing up the rear is Charlie Traversham-Beechers, a charming and well-spoken stranger. Invited to join the birthday dinner, he initiates a savage parlour game called "Hinds and Hounds". It's a stunt that soon has the Torringtons yapping like dogs. Meanwhile, nine-year old Smudge has taken advantage of the adults' inattention to smuggle her beloved pony, Lady, into the house and up to her bedroom.

But for the fact that Jones can't write a bad sentence, the novel's outlandish denouement might have fallen flat. Instead it's hard to forget the anarchic mayhem created by the febrile travellers. Smudge gets Traversham-Beecher's ticket from the start. But she has more immediate concerns when Lady turns skittish at the head of the stairs.

It would spoil the ending to reveal how the Torringtons come to end the night. Suffice to say that Jones's highly combustible period piece makes the dramas at Downton look like a stroll in the park.