Rainbow's friend Rebecca gets mono ("the kissing disease"), and after helping her out, she becomes interested in the medical field. Alicia fibs to Paul about getting a flu shot, and when Denise gets sick, their distrust of the medical community comes to light. Meanwhile, Johan and Santamonica go to live with Harrison while Denise is sick and start to enjoy his lavish lifestyle.

After learning that scientists predict the ozone layer will be depleted in 20 years, Rainbow panics and tries to implement Earth Day at school to influence some change. To her surprise, she is met with resistance, forcing her to takes matters into her own hands to fight for the cause.