A couple of weeks ago, Edgar Dworsky walked into a Stop & Shop grocery store in Somerville, Mass., like a detective entering a murder scene.
He stepped into the cereal aisle, where he hoped to find the smoking gun. He scanned the shelves. Oh no, he thought. He was too late. The store had already replaced old General Mills cereal boxes — such as Cheerios and Cocoa Puffs — with newer ones. It was as though the suspect's fingerprints had been wiped clean.