What is the plot of the story?

Animorphs - The Message by K. A. Applegate is the story of five friends who are Animorphs or humans who can take on the form of any animal that they have DNA mapping for. The story begins with the protagonist, Cassie, who is morphing herself into a squirrel. She wants to be small enough to hide and watch for the predator who has been coming into the barn on her family's farm at night and stealing birds that she and her father have been trying to nurse back to health.

Please post your questions separately.