How did that change? Why? I can't tell you, but the item that was stolen is in an antique shop, not a museum, and the setting isn't Manitowoc but Green Bay. The person who recognizes the contraband is Lars, not one of the sisters. The result is still trouble, so that's all good for a mystery.
My next idea could be one suggested by a woman at a book group I attended. They'd read one of the books, and she had an idea for a future story. In our area (northeastern Lower Michigan), there's a lake that disappears from time to time, drying up and then gradually refilling due to the karst structure underlying much of the area. The suggestion was that a crime might be uncovered when the lake dries up, and the Sleuth Sisters would be called in to investigate.
How will all that work into a story? I don't know yet, but the idea is a great one. Stay tuned!