"Gregor and the Curse of the Warmbloods" is a fantasy novel by Suzanne Collins, published in 2005. It is the third book in the "Underland Chronicles" series.

The story follows twelve-year-old Gregor and his sister Boots as they return to the Underland to help find the cure for a mysterious illness that is spreading among the humans and warmbloods. Along with their friends from the previous books, Gregor and Boots embark on a dangerous journey to find the cure, facing many obstacles and enemies along the way.

As the group travels deeper into the Underland, they discover a new and dangerous enemy, the Bane, who is manipulating events to his advantage. Gregor realizes that he may be the key to defeating the Bane, but he must first learn to control his own emotions and fears.

Throughout the book, Collins explores themes of loyalty, courage, and self-discovery. Gregor must learn to trust his own instincts and make difficult decisions, all while trying to protect his family and friends. The characters also struggle with the idea of sacrifice and the weight of responsibility.

Collins' vivid descriptions of the Underland and its inhabitants immerse readers in the fantastical world, while also addressing real-world issues such as prejudice and discrimination. The book also touches on the topic of genetic engineering, as the illness affecting the warmbloods is the result of scientific experiments gone wrong.

Overall, "Gregor and the Curse of the Warmbloods" is an engaging and thrilling addition to the "Underland Chronicles" series, showcasing Collins' talent for weaving complex themes into a fantastical world filled with action and adventure.