O'Brian's superb series on the early-19th-century adventures of Jack Aubrey, a Royal Navy officer, and his friend Stephen Maturin, Navy surgeon and naturalist, continues with a look at the darker side of Maturin's life: his work in British intelligence. Aubrey, Maturin and Diana Villiers (Maturin's fickle and enigmatic love) are passengers on a packet ship from Nova Scotia to England when two American privateers give chase. They are hunting Maturin, who has compromised U.S. spy networks. The Americans are eluded, and upon reaching England, Maturin sets off to France. Armed with safe conduct papers, he lectures on natural history and installs Villiers in Paris. Suspicious French agents try to bait Maturin but he refuses to be lured into an indiscretion. On his return to London, Maturin is sent to woo Catalan officers and troops from the French cause to the British. Aubrey provides transport, but despite his best support, including staging a splendid charade chase on the water, the mission takes a nasty turn when their ship founders; seized by the French, Maturin and Aubrey are hauled off to Paris's infamous Temple Prison. (Jan.)