Annabeth was chosen by her mother to attempt to retrieve the Athena Parthenon. She wanted to travel to Rome, but many things stood in her way. While Leo was possessed, he fired on the Roman camp. The Romans prepared for attack as they fled on the Argo II. Also, there was a time limit before Gaea rose. So Annabeth finally got to Rome and located the Athena Parthenon, and fought Athena's worst enemy, Arachne. Dionysus and Annabeth's friends arrived at the perfect time, defeated Arachne and sent her all the way back to Tartartus, but something went wrong.
I liked this book because it was all about Greek myths. Also, I liked all of the subplots and glimpses into what was happening with the Romans and Camp Half-Blood through dreams.