A young gentlewoman, Margaret de Beauchamp, finds her fate twisted into the lives of the up-timers when she meets the Americans imprisoned in the Tower of London. In exchange for her help, Rita Simpson and Harry Lefferts give her a huge sum of money to keep her family's manor and its woolen trade from falling into the hands of the crown and its unscrupulous minister, Lord Cork. But Margaret's troubles are not at an end. Her family's fortunes are in a downward spiral. Her trip to Grantville brings unexpected dangers and a possible up-time solution.

Inspired by books in the Grantville library, Margaret has an idea to restore her family's fortunes with an innovation never before seen in fabric design. With the help of Aaron Craig, an up-timer programmer using aqualators, water-powered computers, they teach her father's craftsmen to create a combination machine loom that can produce a new type of woolen cloth. The ornate and perfect patterns quickly trend among the nobility. However, the Master Weavers of the county's Weaver's Guild aren't happy about being overshadowed by the changes to the status quo, and take their grievance to Lord Cork, who is still looking for the people who helped the Americans escape from the Tower.

Cork isn't interested in squabbles between mere tradesmen, but he is very interested in taking over the new calculating machine that is fueling the upsurge in the de Beauchamp fortunes. He sends agents ordered to stop at nothing to secure it for his own ends. Margaret has to protect her new business, and prevent anyone from discovering that up-timers are in the country to assist her, but she still has to deal with an uprising at home.