Off the Rails (Shades)

Can two boys solve a mystery they were never supposed to know about?  Karl is on the train going home from school when he sees two men dumping a rolled up carpet into a ditch. Karl notices a scruffy shoe sticking out of one end. After telling the police, who don't seem to be that interested, Karl drags his friend Daniel to the ditch to investigate further—but they are soon disturbed by two unsavory characters.