Dr. Peter Blood, a skilled physician working in Somerset, England, is wrongly accused of treason when he is discovered helping a wounded man during the Monmouth Rebellion against King James II. Despite his protests of innocence, he is swiftly tried and convicted, and sentenced to death. However, his sentence is later commuted to life imprisonment and he is sent to the West Indies as a slave.
During the slave transport, Blood meets with other prisoners who become friends and allies. When the ship carrying them is attacked by the Spanish, Blood and his comrades overpower the Spanish crew and escape on the emptied ship. They become pirates, attacking French and Spanish ships and gaining wealth and fame as their exploits spread.
Eventually, Blood and his crew capture the ship of Arabella Bishop, the niece of the cruel and ruthless Governor of Jamaica, who is travelling to the colony to marry a plantation owner. Blood takes a liking to Arabella and convinces her to help him trade their captured goods in Jamaica, where he hopes to find a way to clear his name.
Arriving in Jamaica, Blood is captured and brought before the Governor. The Governor offers clemency in exchange for Blood's future loyalty to the English Crown, but Blood refuses and is sentenced to death. However, he is rescued by his crew and Arabella, who helps him arrange a clever escape.
Blood and his crew continue their piracy, but eventually, they receive a pardon from the King of England. Blood and Arabella reunite, and he is given a commission in the Royal Navy. He is later appointed Governor of Port Royal, Jamaica, where he proves to be a just and fair leader.