In 1761 the cousins King Louis of France and King Charles of Spain agreed in secret that Spain would enter the war against Britain by spring of the following year.
Edward Carlisle’s ship of the line Dartmouth is sent from Jamaica on what looks like a trivial mission intended to demonstrate friendship to Spain. However, in Havana he finds evidence of growing co-operation between the French and Spanish navies. While carrying the new governor of Guatemala to his domain he uncovers further plots, and his wife, Lady Chiara, uses her talents for languages and diplomacy to earn a seat at the ship’s councils of war.
Carlisle’s search for evidence of preparations for war takes him further west into the Gulf of Mexico, and to a final battle with a more familiar enemy.