Full Speed: Kensy and Max Book #6 by Jacqueline Harvey
After a school excursion goes horribly wrong, Kensy and Max are left with a sneaking suspicion that the incident was no accident. But there’s no time for investigation as the twins are whisked away to Switzerland on a fully sanctioned Pharos mission.
Upon landing in Zermatt, Kensy and Max are tasked with infiltrating the Van Leer family. Strange as the Van Leers are, proof of their misdeeds is scarce. And when a surprising figure appears in the ski town, it seems there is more than one mystery to solve. Kensy and Max are on a mission for justice and won’t stop until it’s served.