Carolyn Keene 
Thrill on the Hill [EPUB ebook] 

A DAY OF SLEDDING SNOWBALLS INTO A BAFFLING MYSTERY!Hurray! The ground is covered with thick snow and that means no school. As soon as Nancy gets the news, she, George, and Bess head straight for the park to go sledding. Everybody is there, including Molly Angelo with her brand-new sled.Molly’s sled is really fast, and everyone wants to borrow it. But after the girls take a hot-chocolate break, they return to find it’s gone! So who took it? Just like snowflakes, no two mysteries are alike — and Nancy better figure this one out before the snow melts!