Howard Weston is a wealthy ship owner and merchant in Plymouth when the English Civil War begins in 1642. Plymouth, as with many English ports, supports Parliament against King Charles I. The story describes Howard's efforts to ensure the Royalist siege of Plymouth fails. The supplies the city needs are brought in by ship. Invative military tactics are used against the Royalist armies. The climax is the successful defence of Howard's home, Encounter Hall, east of Plymouth.