Jim Stringer, the nice young Edwardian railwayman and amateur sleuth from Andrew Martin's much-praised previous novel, The Nec-ropolis Railway, is back. Back up north, actually. It is 1905 and Jim has left the Smoke to return to his native Yorkshire as a fireman on the "Lanky", the old Lancashire and Yorkshire Railway. Meanwhile the character he used to call "my landlady" has become "the wife": "Marriage suited me very well in a roundabout sort of way. I liked being with the wife, and I also liked being away from her, for a short while at least." Because of her former calling you might imagine the wife as a dragon, but Jim keeps reminding you that she is in fact a beauty.

Despite his changed circumstances, Jim is much the same - inquisitive but dopey, apt to go off on wild-goose chases and get cracked over the head by members of the criminal classes, who are considerably bigger than he is.

This present investigation is set off by a fatal incident for which Jim himself is partly to blame, so he is motivated by guilt as well as curiosity. On Whit Sunday, he and his driver, Clive Carter, have to take an excursion train full of mill em-ployees from Halifax to Blackpool. They are assigned one of the Lanky's top express engines, a Highflyer. It happens to be engine Number 1418. You wonder if Andrew Mar-tin picked that number to give the reader a subliminal sense of im-pending doom: however many scrapes Jim may survive in this and no doubt in future novels, the relatively stable and happy world around him will end in the catastrophe of 1914-18.

The guard comes to tell Jim and Clive: "512 souls, 220 tons." He always tells them the load. Unusually for an excursion, there's a first-class coach on, with the mill owner and his ancient father travelling in state. The train sets off, Clive notches up the power and they're fairly streaking. "It was a great lark," Jim says, "but 1418 was wearing me out - not from the amount of coal wanted, but from the need to keep braced against the rolling."

The Highflyer got its nickname because it was built too high. The driving wheels were more than seven feet in diameter. With the boiler perched on top, the whole thing not only looked peculiar - "a giant baby carriage", in Jim's view - but it also had a distinctly rocky motion at speed.

It's not the engine that causes the trouble, though. It's the bloody great grindstone someone has put on the line in the middle of the 80mph strait just before Blackpool. Sharp-eyed Clive slams on the vacuum brake and the reverser and the train stops; only the front bogie wheels are derailed by the stone. Disaster averted. Unfortunately, a mill girl, standing to reach the luggage rack, has been hurled across her compartment by the violent braking and has banged her head. She is semi-conscious, and vomiting.

Against another passenger's advice, and without consulting the first-aid manual until too late, Jim decides that the thing to do is to sit her upright. It kills her.

Over the succeeding weeks, Jim obsessively schemes to unmask the saboteur. Was it the recently dismissed director of the mill, the apparently good man who hired the wife as a typist? Or one of the Socialist Mission agitators in Halifax who claim mill excursions are a capitalist sop to put off the revolution? Or the stationmaster, whose wife the deb-onair Clive may be seeing on the sly? Or, as an inspector was on the train, was it someone involved in the complex ticket fraud that Jim's lodger, a booking clerk, warns him about? Or was the intention to derail the scheduled express coming behind the special, in which case none of the above would be relevant?

Along the way there are several flavourful scenes in the streets, pubs and music halls of Halifax, Blackpool and Scarborough. Some of the period detail is over-intrusive, but some of it is casually vivid: trailing a suspect, Jim shelters from a cloudburst "in front of a butcher's, with a line of dead rabbits over my head holding the rain off". (All butchers used to have those out-front displays, long since banned.) As in The Necropolis Railway, the plot is only moderately well organised and the story tends to become a series of vignettes; but it is another atmospheric experience, a trip to a lost world in amusing company.

Hugo Barnacle is a novelist and critic