Detective from the Seventh D. A Tale

Seventh "D" student Clarissa Mironoff loves detective novels. She can solve even the most complicated case at school. But now she will have to try harder, as her best friend Masha is facing big trouble.
What connects a math test, the café "At the Mad Hatter," a dodo bird, and a quiet, lovestruck honor student? What does the first school fashionista have to do with it? And most importantly, how to distinguish a friend from an ingenious criminal?..