The play was most likely written c. 1636, while Killigrew was travelling in Italy, and was acted on the stage c. 1638, by Queen Henrietta's Men at the Cockpit Theatre.
Tragicomedy, coloured by Neoplatonism and Platonic love influences, was the fashion in which courtier dramatists like William Cartwright, Sir John Suckling, and Lodowick Carlell were casting their dramas in the 1630s.
Though written and acted late in the Caroline era, The Princess was not published until its inclusion in Comedies and Tragedies, the collected edition of Killigrew's plays issued by Henry Herringman in 1664.
One consists of Facertes, Cicilia, and Lucius, the children of the late king of Sicily; and the other, Virgilius and Sophia, the (wildly fictitious) son and daughter of Julius Caesar.
Caesar has attacked an independent Sicilian kingdom; its king was killed in battle, and his son and heir Facertes taken prisoner.
Facertes has been placed in the custody of Caesar's son Virgilius, who, commanding troops in the Gallic Wars, was not involved in the conquest of the island.
Stopping in Naples, Virgilius sees a beautiful young woman in the slave market there, and instantly falls in love with her.
A local woman named Paulina has watched the unfolding events; she has fallen in love with Virgilius, and hides him in her house.
Meanwhile, Cilius has failed in an attempt to purchase Sophia's freedom; to save her from the Neapolitan slave market, he sets the Roman prisoners free and escapes, with them and his followers, on a galley of his own.