Case Files 19 & 20: The Case of the Gobbling Goop & The Case of the Surfer Dude Who's Truly Rude
Enid Blyton
There are two stories/TV episodes in each book so they are 'flipper' books, with a front cover for each story. THE CASE OF THE GOBBLING GOOP An eccentric professor disappears - with a secret formula! THE CASE OF THE SURFER DUDE WHO'S TRULY RUDE Surfboard sabotage in Malibu!