From End of Casefile#5 -- Frank and Joe know that "Uncle" Hugh Hunt isn't really an uncle. He's an old friend of their father's -- an insurance salesman, and to tell the truth, a bit of a bore. So why would anyone feed him a slow-acting poison? The Hardys have only three days to find out. And as they investigate, Frank and Joe find spies, theives, and some things about UNcle Hugh that they never suspected. They also discover the plans for a major jewel robbery. Will Frank and Joe be forced to break the law to save a life?

From back cover: -- When Frank and Joe join their uncle Hugh for lunch, the main course turns out to be a bizarre kidnap plot. After a violent scuffle, Uncle Hugh is whisked away, and the boys suddenly find themselves in deep trouble with a U.S. espionage unit. Special Agent Starkey is out to prove Hugh is a traitor and accuses the boys of helping him escape. To complicate things, a beautiful mystery woman called Charity is also on their uncle's trail. Meanwhile Frank and Joe are stranded in a strange city far from home, being hunted down by two desperate gangs -- with orders to shoot to kill.