Fresh off the chaos of Jackson's prototype crash, Attie McAllister is juggling recovery schedules, mysterious HELIOS blueprints, and the mounting pressure of her first major STEM talk. With her mom training in Houston, her dad pursuing a cyber investigation overseas, and Aunt Loxley uncovering dangerous clues, Attie's managing more moving pieces than ever, and somehow, she's thriving. As the girls dig deeper into the secrets of "The Six," cryptic notes point to an unknown architect and a possible description of the fourth member, someone who may have been designing a revolutionary hydrogen-powered engine. The past unfolds through sketches, ciphers, and stories no one expected, and these blueprints might hold the key to something far bigger than a buried research project. But as new clues illuminate the trail, familiar questions resurface: Who's been hiding the truth? Why was HELIOS deliberately split apart? And what role will Attie play in putting it all back together? STEM-powered, sass-infused, and full of heart, Book 4 of the Charms Book Series takes readers deeper into a legacy of invention, resilience, and brilliant young women learning to lead - with their minds, their voices, and their unstoppable curiosity. Life Skill Focus : Code Breaking Foreword By: Cindi Branham Meet the Series That’s Inspiring Girls Everywhere! Book Order 1 Rocket City Love – Every inventor’s story starts with a spark. 2 Tick Tock, Take Charge! – Adventure doesn’t come with a pause button. 3 Where Clues Take Root – Decode the past. Protect the future. 4 Blueprints & Buried Truths – From hidden ciphers to hydrogen power, the secrets of HELIOS rise. 5 Calculated Risks – The formula for courage: friendship + truth + risk. 6 The Gravity of Choice – Decisions have gravity. Attie’s could shift the future. 7 Legacy Protocol – HELIOS was never lost—it was waiting for her. Download & Learn by Doing — Just Like Attie Each book includes a download (available at the Charms Book Series website) to help readers apply Attie’s real-world life skills: time management, leadership, budgeting, pitching, and project planning. Learn by doing and see how STEM and storytelling connect! Your Purchase Makes a Difference By purchasing this book—or any Charms merchandise—you’re supporting Athenian , a STEM edu-tainment nonprofit dedicated to empowering girls through hands-on learning, storytelling, and real-world adventure. Every Charms purchase fuels our mission to build confidence, character, and curiosity in the next generation of innovators. Together, we’re shaping the future—one story at a time. If you like Tree House Mysteries, The Baby-Sitters Club, Nancy Drew, Carole Marsh’s mystery books, National Park Mystery Series, The Math Inspector series, then the Charms Book Series is the natural next step. Those favorites deliver friendship, adventure, and curiosity and Charms keeps that same feel while leveling up for ages 8–14 (grades 6–9) with older characters, deeper thinking, and real problem-solving. This juvenile fiction / middle grade chapter book series for girls blends mystery and STEM-ready curiosity with life skills like decision-making, confidence, responsibility, and leadership making it perfect for reluctant readers, libraries, book clubs, and parents who want fun, safe stories that quietly strengthen literacy. Still funny. Still wholesome. Just a little more “you’ve got this” and a lot less hand-holding.