Martin, Crystal and Troy Buchannan go undercover when a chemistry teacher and his family are kidnapped. The case takes on urgency when it's feared the kidnappers will use the teacher to manufacture a deadly gas.

Martin poses as an international arms dealer to rescue kidnapped chemist Richard Hubbard and track the sale of VX gas. Before long, he connects with a beautiful arms trader and slips into a shadowy romance with her.

Martin is sold VX gas, resulting in the apprehension of the Colonel and Ana Paulanos. In response, one of the Colonel's minions releases VX on a crowded bus, and promises more attacks if the Colonel and Ana aren't released.