The McGurk Organization gets into the big time when the kids are hired by one Mr. Fitch, an ex-U.S. secret agent now purportedly writing his memoirs. Fitch, who needs the kids as couriers because he himself has broken his leg, gives them a cock-and-bull story about needing to prove his ""drop"" and ""pick-up"" skills in order to get help on his book from another former spy. But a grease spot on both incoming and outgoing messages tips off the bright young detectives that there is something fishy about Fitch, and a peep at one of the packages confirms their suspicions: it contains not a coded message but torn halves of ten hundred-dollar bills. Is Fitch a drug dealer, as the kids then suspect? No, but he is breaking the law, as an industrial spy stealing plans for a copy machine. The detectives have to think fast as the police (alerted by the Organization) close in--but then they've been kept on their toes from the start by the nifty code challenges. Readers will be too.