The Missing Chums (Hardy Boys, Book 4)

Two of the Hardy boys' chums take a motor trip down the coast. They disappear and are almost rescued by their friends when all are captured.

• The Secret of the Old Mill (Hardy Boys, Book 3)
• Hunting for Hidden Gold (The Hardy Boys, No. 5)
• The Shore Road Mystery (Hardy Boys #6)
• The House on the Cliff (Hardy Boys)
• The Secret of the Caves (Hardy Boys, Book 7)
• The Mystery of Cabin Island (Hardy Boys, Book 8)
• What Happened at Midnight (Hardy Boys, Book 10)
• The Great Airport Mystery (Hardy Boys, Book 9)
• The Tower Treasure
• While the Clock Ticked (Hardy Boys, Book 11)