Hong Kong on and off-screen partners Mabel Cheung and Alex Law are planning a giant leap in budget for their next production, provisionally titled The Story Of Ah-Toi, to be set in the US and written and directed by Law with Cheung producing.

Throughout their career together, Law has written and Cheung directed An Autumn Tale, The Soong Sisters, Beijing Rocks and the upcoming $1.5m Cultural Revolution drama Red Shoes, while Law has directed the Jackie Chan/Sammo Hung biopic Painted Faces. Now, they're aiming to up the ante to $5m for a period epic set during the US railroad construction in the early 19th century.

And the story of Ah-Toi is quite a story: with some 5,000 Chinese men working on the railroads in the US, denied access to their wives and families, Ah-Toi was a real-life hooker who somehow managed to get herself in pole position to not only service the legion of railroad workers but act as their interpreter when it came to official business.

Law, who plans to shoot the epic in Utah or San Franciso and is looking to raise backing for what he envisages to be a co-production between a Hong Kong company and a US one. "This project is going to be like The Soong Sisters - it will take a long time," said Law.