Here's the gist:
* Percy and Annabeth are captured by the Furies. They're being taken to the Underworld, where they'll be judged by Hades.
* Annabeth hatches a daring escape plan. She uses her knowledge of Greek mythology to figure out how to get out of the Underworld using Cerberus, the three-headed dog.
* They use their wits to appease Cerberus. Annabeth distracts him with a golden apple, while Percy makes a deal with him to deliver a message to his master.
* They successfully escape by riding Cerberus back to the surface world, leaving the Furies behind.
This chapter highlights Annabeth's intelligence and problem-solving skills, as well as Percy's resourcefulness and ability to connect with creatures. It also introduces Cerberus and foreshadows the significance of the Underworld in the story.