Magic Pony Carousel #4: Jewel the Midnight Pony by Poppy Shire

The Magic Pony Carousel is in town! Sophie is excited to ride Jewel, a jet black pony with a beautiful diamond-shaped white patch on his forehead. As soon as Sophie settles into Jewel's saddle, they are whisked back in time on a magical adventure. Together, Sophie and Jewel must capture a villain, return a stolen locket, and rescue their new friend, Lucy!