A geek, and proud of it, twelve-year-old Pete is determined to win the school science fair in an effort to convince his sports-enthusiast dad into accepting science as a worthwhile endeavor and for once be proud of Pete. Upon discovering a giant seed in the forest, Pete figures he has the grand prize wrapped up in a nutshell. When the seed sprouts into a baby, the science fair is off—no one can know the truth about Pete’s newly “adopted” brother, Sprout. Not even his dad. But when Sprout grows at an alarming rate, his skin turns green in the sun, and he exhibits super-hero-like plant powers, Pete knows he won’t be able to protect his new brother for long from those who would view Sprout as a threat. To make matters worse, Pete fears his dad likes Sprout more than him.