The Chocolate-Covered Contest (Nancy Drew Digest, Book 151)

Nancy is about to learn the real meaning of "Death by Chocolate"
Nancy can hardly believe it. While visiting an amusement park owned by the world-famous Royal Chocolates Company, her friend Bess tears open a million-dollar candy wrapper in a contest. But when they go to collect, they're told that someone else has won. And then they're accused of tampering with the winning wrapper!
Something is rotten in chocolatetown. The proof comes when Nancy and her friends are treated to a near-death experience in the park's animal safari. Someone's pulling a million-dollar swindle, and getting Nancy and her friends out of the way seems to be the icing on the cake.