The Assassin and the Underworld is the third of four novellas which outline Celaena Sardothian's adventures before the events of Throne of Glass which is debuting in August. This third novella picks up where the second one left off, with Celaena returning to the Keep after a summer away. She has to navigate through her uncertain feelings for her fellow assassin Sam, her desire to be free of the King of Assassins and the technical details of her latest mission. From the Keep to the Opera, Sarah's world is fleshed out all that more as is the relationships between Celaena and the people that she knows.