The Hardy Boys series, first published in 1927, has sold more than 70 million copies!Now with a brand-new look, this is an edition that collectors won't want to miss! In The Secret of the Caves, the seventh book in the incredibly popular, long-running series, Frank and Joe Hardy discover the secret of the Honeycomb Caves while searching for a missing professor. A special treat for Hardy Boys fans and any reader who's new to the series!