The hardback version of the story, which has been snipped for paperback About four years ago, two Oxford authors met over a cream tea at the Old Parsonage Hotel and the plot thickened.

They set about solving a problem that has been troubling some authors for centuries - how to write a bestseller.

William Horwood, a former journalist specialises in writing fantasy fiction, while Helen Rappaport started her career as an actress, before turning historian, with books on Stalin and women social reformers.

The idea was that they would combine their talents to write a historical thriller. And the setting?

The pair decided to ignore the genteel backwaters inhabited by Morse and Lewis and head for more menacing territory - Chicago in 1893, when it hosted the World's Fair.

Here's the pitch. When Anna Zemickis, a young New Yorker goes missing in Chicago, Emily Strauss, an inexperienced but ambitious reporter with Pulitzer's World, is given the task of finding out what happened to Anna and other missing women.

The story then takes place over 11 days in October, and I was gripped by the plot as it becomes clear that Anna is not dead, but is very much alive, and trying to escape the clutches of a dangerous group of businessmen butchers known as the Meisters.

Throw in women's rights, immigration and pornography, and there is plenty of food for thought for the reader who wants a bit more than the basic murder mystery.

Helen, who also has a book coming out about the Romanovs, told The Guide: "The story was first published in hardback last year as Dark Hearts of Chicago and the paperback is about 50,000 words shorter.

"The cuts were substantial and were made to sell the book in America. A lot of the historical research I carried out was cut, but the pace is much better.

"We would have liked to have used our own names, but publishers loathe titles with two named authors so the pseudonym James Conan was chosen, although I would have liked a female pseudonym. William and I made two research trips to Chicago and I like to think we have really captured the feel of just how dynamic a place the city was in the 1890s."

The historian says heroine Emily Strauss was based on real-life Americans such as Helen Cusack, Elizabeth Jordan and Elizabeth Cochrane, who came from small towns and talked their way into jobs at big newspapers.

They became known as the stunt girls, who would do anything, including working undercover as rag-pickers, beggars, or even prostitutes.

Her co-writer believes City of Dark Hearts has benefited from the collaboration and the pair even turned down a deal with an American publisher, because the editors wanted to slash a further 25,000 words.

"It's a different market in America - the European reader is used to a more subtle kind of storytelling - and we were not prepared to play ball," said William.

The 63-year-old is convinced the novel will get published in the States, once it starts to sell well in the UK.

The cover of City of Dark Hearts - featuring a man in a bowler hat and long coat watching in the shadows - looked rather familiar to me and then I realised where I had seen him before.

He also makes an appearance on the jackets of Carlos Ruiz Zafon's The Shadow of the Wind and on Jed Rubenfeld's The Interpretation of Murder.

If Dark Hearts of Chicago can start to match their sales, then it will be cream teas all round.

City of Dark Hearts is published by Arrow Books, price £6.99.