Monty Hall #5

In the main story "Monty Hall of the U.S. Marines," Monty and his fellow Marines encounter enemy agents posing as soldiers and uncover a spy ring operating within their ranks. After discovering that a man named Proto is involved in espionage, Monty and his unit must locate him and a secret passage hidden within their quarters before the spies can escape. The story culminates with Monty and the Marines pursuing the suspects and confronting them about their true identities and motives.