Hardy Boys The Secret of the Caves #7, Book 7, (Hardcover)

The Hardys are dealing with two cases. While their father works on sabotage at a local security station, Frank and Joe head to a college to try to find a missing professor. But the trail leads them to some caves south of Bayport. What exactly will they find there? This was actually the first Hardy Boys books I picked up many years ago, and it was fun to revisit. I didn't remember much about the mystery, so it kept me guessing until the end. I did find the ending very rushed and the characters flat, but I still had fun revisiting them.