Plot

In this book the Hardy boys (Frank and Joe) are asked to help stop a world-famous spy who works for the HAVOC, an international network of terrorists, wants to defect to the U.S. Frank and joe know the spy as "Igor”.

Also a million-dollar emerald from South America has vanished. Joe and Frank think “Igor” was involved. Their only clue is mysterious symbol in shape of tic-tac-toe. The game lead to a building that is run by the U.S government. The building has a bomb and the Hardys are trapped in a deadly game of tic-tac-toe.

• Publication date: 1982