A few years had passed, and after too many disappointments, the Cutie Mark Crusaders group has fallen apart. The fillies abandoned hope in getting their cutie marks by constantly trying something new, and instead followed the path of standard, boring careers. Their lives are about to take a big twist as they get on track of a serious crime.

Mystery and adventure, now with books!
Twilight Sparkle's weekly book shipment arrives one book too big. Among the others, there's a handbook about pony genetics. Curiosity leads her to an interesting discovery.

Sequel here