Sid the roving reporter is investigating something strange in his backyard--his Dad is wearing a mask while painting. Sid discovers that his Dad is protecting his face so he doesn't breathe in the dirty fumes. At school, Sid and his friends discover that people and animals on Earth need to breathe clean air, and when we pollute the air around us, it affects the air that everyone breathes. The kids also discover that trees have a really important role in keeping our air clean!