The clue at the bottom of the lake

It’s The Middle Of The Night When Jeff Spots Someone Dumping A Large Bundle Into The Lake. It’s Too Dark To Identify Anyone — Or Anything. But The Cousins Immediately Suspect Foul Play, And Plunge Right Into The Mystery. Before They Know It, The Kids Of Cabin Creek Are In Too Deep. Everyone Is A Suspect — And The Cousins Are All In Danger!–p. [4] Of Cover.