Workers discover a time capsule at Lincoln Elementary, but it's locked! What could be inside? Whoever made it left a trail of geometry clues based on shapes. Be a math detective along with the kids at Lincoln Elementary and help solve this pick-your-own-path mystery. Choose the right answer, and advance to the next clue. Choose the wrong answer, and clear text and visuals explain the math and encourage you, the reader, to try again. Friendly illustrations with a diverse cast of relatable characters will engage readers, while clear math explanations support CCSS standards for second-grade math.