"Sophie" is sent to accompany a small convoy of merchant ships in the Mediterranean. Aubrey takes the opportunity to get to know his sailors and work them into a fighting unit with the aid of his new first lieutenant, James Dillon, a wealthy and aristocratic Irishman. Dillon and Maturin had met earlier (a fact they keep to themselves) as members of the United Irishmen, a society dedicated to Irish home rule and Catholic emancipation. Dillon suffers a crisis of conscience when ordered to intercept an American ship thought to be harbouring Irish rebels, and he works to help them avoid capture.