What happens when the Hardy parents are away and a mystery appears. Do the Hardy boys wait until their parents come home? Heck no!!
The same themes in the previous 11 books return. It has the recipie for being a yawner but it is suspensful instead. A very good read. ( )

Yet another wealthy eccentric Bayport resident, yet another barmy inventor, yet another mystery for the Hardys to solve. Raymond Dalrymple asks Frank and Joe to help explain the threatening messages which keep appearing in an impenetrable time-locked room deep in his newly-bought house. It's essentially a MacGuffin, however, the "why" of which is obvious relatively quickly and the "how" of which takes until the end of the book to explain and is almost anti-climactic in its resolution. In the meantime, however, there are a gang of harbour thieves to worry about, which means boat chases, car chases and punch-ups a-plenty.
Quite silly really in many parts, it's still a pacy adventure for the Hardys and not the worst by any means. ( )

Will did a book report on this one.