This question is rather wide and open to more than one interpretation. However, for the purposes of simplicity, I will refer to important details onboard the Cutty Wren (the ship that has the hopes of England). Captain Samson is preparing to set sail when he receives an unexpected visit from Sir Geoffrey. Sir Geoffrey introduces him to Mr. Black—a member of the Crown's special unit known as the Gentlemen of Last Resort. They need Captain Samson's ship to go and retrieve a new heir for England at Port Mercia. Mr. Black tells Samson that the king and both his heirs have died from influenza, and to avoid war or an invasion from France, they have to declare a new king within nine months, since those are the rules in the ratified Magna Carta.