It is two years since Thomas Kydd was spirited away in the night to serve his country aboard the old line-of-battle ship Duke William. Now, he and and the other members of the ill-fated Artemis are shipwrecked sailors, back in London waiting to be summoned as court martial witnesses. Then, in a political act to shield an officer's reputation, they are shipped out in haste to the Caribbean - where sugar is king and yellow jack a fearsome peril.