Risk — Brock Eastman

Flying to coordinates unknown, the Wikk kids land the Phoenix on planet Evad and descend into an ancient jungle. Revealed is a highly intelligent civilization, once inhabitants, but now vanished, leaving behind astonishing technology! High stakes lead the Wikk kids on a dizzying ride from the pinnacle of a ziggurat into an endless underwater labyrinth. Dive into adventure, as the twins face a deadly showdown with the evil Ubel! Can they win the struggle to survive the savage snares, with the help of the elusive, Brother Sam?
The Quest for Truth series follows the four Wikk kids in their desperate race to find the mysterious planet Ursprung and stop the Ubel renegades from misusing its long-lost secrets. Ancient cities, treacherous villains, high-tech gadgets, thePhoenix -- encounter all these and more on this futuristic, interplanetary adventure.