Kester Jaynes
Kester Jaynes is a 12-year-old boy who has been imprisoned in Spectrum Hall Academy for Challenging Children for nearly half of her life. Since his mother died, Kester has not been able to speak. Although he wants to speak, he is not able to put his thoughts into words.
In the Academy, Kester keeps mostly to himself. He keeps the company of animals, including a cockroach, who he is surprised to learn that he is able to communicate with. In fact, Kester is able to communicate with a wide range of animals, a rare gift.
Kester is determined to find a cure for the virus that had decimated much of the animal population - hopefully before Facto kills all remaining animals in an effort to stomp out the Red Eye Virus.
Polly
Polly is a young girl who Kester meets during his journey. She is one of the two main characters in the book and is a compassionate, driven, and hard-working person who witnesses a number of scary things during her journey. She is also very trustworthy and loyal, as she is determined to help Kester through his journey to stop the Red Eye virus and stop the deaths of animals at the hands of malevolent forces.
Animals
Because of Kester's unique ability to communicate with animals, quite a few animals - including a cockroach, for example - are vital characters in the book who give Kester comfort and help him accomplish his goal.