Hodder & Stoughton has bought a "groundbreaking digital serial Western", Nunslinger by Stark Holborn.
Anne Perry bought world rights in a deal with Ed Wilson of Johnson & Alcock.
Set in 1864, the story sees nun Sister Thomas Josephine on her way to California, and finding she has to pick up a gun, in a plot featuring "varmints, lowlifes, cowboys, drifters, desperadoes, high-plains adventure and page-turning excitement".
The story will be published as a 12-part serial digital original, with parts 1, 2 and 3 published on 26th December 2013 and nine more parts following in March, June and September 2014. Nunslinger is to be promoted with a "spectacular" digital campaign across online communities starting on Boxing Day 2013.
Author Stark Holborn is said to be "shrouded in mystery", with Nunslinger "his or her" first published work.
Perry said: "I’ve loved Westerns since I was a kid, and I couldn’t be more delighted with Nunslinger. It has all the action, adventure, drama—and even a little romance—that anyone could want, and I’m thrilled to be able to publish it in true 19th-century style: serially.
"Hodder has a long and proud history of publishing Westerns, from Zane Grey to Max Brand, and I’m thrilled to be adding another classic to the fold. This is a Western for the 21st century."
Wilson said: “It’s not every day a Wild West enigma slams a bottle of Jack down on your desk and starts telling you what happens to the human brain when shot at close range with a shotgun. But when that day comes, you know you’ve got to grab it with both hands.”