Burnt Mountain One in the Chamber — Cheryl Campbell

Rio Kaiser's day off from school turns to disaster when Ilnin and his hunters escape the world hidden beneath Burnt Mountain. She avoids capture, but her mother and father aren't as lucky. Rio plans to use her usual ability to control the elements during her return to the underground world of living nightmares to find and rescue her parents, but everything goes wrong when she ends up in the prison cell next to them.
Injuries and illness strike, and Rio's friends and family begin turning on each other. She is unable to help them while her worsening hallucinations threaten everyone's chance of escape, including her own.