It's a mystery worthy of Agatha Christie.
In the early hours of October 13, 1928, the Leeds to Bristol night mail train was making its way quietly towards its destination.
The fog that night was thick and as the train, with 50 passengers on board, passed through Gloucestershire the driver and his fireman didn't see the warning signal ahead.
Within a matter of seconds, a routine journey had turned into a national disaster. Ploughing into a freight train, one coach was thrown across a bridge and when the gas cylinders used to fuel the lights exploded on impact, the 40ft high flames could be seen from miles around.
Emergency services arrived quickly on the scene, but for many of the passengers it was already too late – 12 of those who died were so badly burnt their families accepted the railway company's offer of a mass grave. For those involved in the rescue operation, the scene was grim, and when the bodies of two young children were discovered among the wreckage they knew someone would have the unenviable job of telling their relatives their worst nightmare had come true.
However, no one ever did come forward. One witness described the pair as well-dressed. Another told police officers they thought the boy was about 10 years-old; the girl, they said, looked a little younger and they had assumed they were brother and sister.
Despite high profile appeals, the pair were never identified and as the years passed the case passed into folklore.
"It's an intriguing tale," says Nick Blackstock, author of Something Hidden, a fictional account of the crash and its aftermath. "I first came across the story when reading the memoirs of the coroner who carried out the inquests and I always thought it would make a fascinating basis for a novel."
In the months which followed the crash, various theories were put forward as to the identity of the two children and some even doubted the bodies had existed at all.
Nick admits trying to get to the truth of what happened 80 years ago is impossible and his novel, which suggests their deaths were part of a cover-up of the very highest order, was completed with a large helping of artistic licence.
"At the time of the crash it was still very much the era of the Empire when many wealthy parents lived and worked abroad while their children were educated here," says Nick, who lives in Keighley. "At first, people thought that was the case with these two children, but no mother or father ever returned demanding to know where their children were.
"There were suggestions part of their school uniform had been found. Apparently, it bore the motto Luce Magistra which is the one used by Queen Ethelburga's near York, but the school always denied any connection to the children.
"The mystery generated an avalanche of letters to newspapers and it was from these the truly off-the wall suggestions emerged. One suggested the remains which were found were in fact those of two ventriloquist dummies and another claimed they were not children, but jockeys.
"For years afterwards a lady in black was also seen visiting the Charfield cemetery laying flowers at the memorial to the two unknowns, but of course no one thought to ask who she was. Rumour had it a Gloucester solicitor also had crucial information about the crash, but like all good mysteries he died without ever telling anyone what he knew."
Having studied history at university, Nick has always had a fascination with the past and his first book Beast was inspired by the true story of a wolf that terrorised southern France in the 18th century. Something Hidden may be set in a different time and place, but it's fuelled by the same sense of mystery.
"There's always a worry when you're writing about historical riddles that before you've finished the final draft someone will come forward and reveal the truth," says Nick. "Thankfully, no one seems to be able to throw any real light on either of the mysteries I've written about and for that I am very, very grateful."
n Something Hidden by Nick Blackstock, priced 9.99 is available to buy through the Yorkshire Post Bookshop on 0800 0153232 or online at www.yorkshirepostbookshop.
co.uk. P&P is 2.75.