J.K. Rowling has been spotted in cafés in the historic Scottish city of Edinburgh working on a detective novel, The Sunday Times of London reports.

The paper quoted Ian Rankin, a fellow author and neighbor of Rowling’s, as saying the creator of the Harry Potter books is turning to crime fiction.

“My wife spotted her writing her Edinburgh criminal detective novel,” Rankin said at the Edinburgh literary festival.

Rowling may be entering a genre dominated by some of Scotland’s greatest storytellers, including Arthur Conan Doyle and Robert Louis Stevenson.

Rowling famously penned initial drafts of her first Harry Potter book in Edinburgh cafes in the early 1990s. She was then a struggling single mother who wrote in cafes to save on the heating bill at home.

Now she’s Britain’s richest woman – worth $1 billion, and ahead of the Queen, according to Forbes magazine – and her seven Potter books have sold more than 340 million copies worldwide.

For more on the Potter success, see: “It’s Hurry Potter: Newspaper editors employ speed-readers to review new Potter book.”