In this book, Crawlers kidnapped Boots. They stole her while Gregor was in Central Park in New York City. They took her to the Underland by going through really steep stairs and tunnels. They took Boots to get Gregor to come so that he could kill the Bane. The Bane was a white rat, and rats are humongous in the Underland because everything is humongous in the Underland. The rats eat meat which means they eat people.
Gregor agrees to go after the rat. Gregor and his group have to go in a boat and then ride in the boat but on their way they met with giant squid that attacked the boat trying to get Gregor. Near the end of their trip they found the giant sea serpents that tried to eat them. The serpents woke up because the rats pushed boulders into the water to wake them up.
You should read this good book. I'm not usually a book fan but I still really like this book because of all the exciting adventures.