Minerva's Voyage

Robin Starveling, aka Noah Vaile, is scooped off the streets of seventeenth-century Bristol, England, and dragged onboard a ship bound for Virginia by the murderous William Thatcher, who needs a servant with no past and no future to aid him in a nefarious plot to steal gold. Starveling fits the bill perfectly since he lives nowhere and has no parents. Aboard the ship, Starveling makes friends with a young cabin boy, Peter Fence.
Together the two boys suffer through a frightening hurricane and are shipwrecked on the mysterious Isle of Devils. They solve the ciphers embedded in emblems found in Thatchers sea chest, which has washed up with the wreck, then make their way through gloomy forests and tortuous labyrinths to a cave on the shore that houses a wizard-like old man. Beset by danger and villainy on every side, they finally discover the old mans identity and unearth a treasure that is much rarer and finer than gold.