An experienced American sea captain undertakes clandestine voyages to carry men and munitions to insurgents, commanding a small steam tug and a mixed crew of rough seamen and expatriate fighters. The narrative moves episodically through shipboard hazards, storms, naval blockades, tense discipline, and occasional violence, testing practical seamanship and leadership. Interactions among professional soldiers, hotheaded patriots, and seasoned crew reveal divided loyalties and moral compromises, while a succession of maritime and shore episodes keeps the pace brisk and emphasizes resourcefulness under pressure.