When Nate Chance arrives home from school, he sees two police cars and an ambulance in his yard. Before his mother can get him and his little sister, Junie, inside, Nate and Junie witness their father, blood pouring down his face, being led by two police officers into an ambulance. He has tried to kill himself.

Home quickly becomes a different place. Junie stays curled up in front of the TV; Nate's mom retreats inside herself; and the rumor of mental illness makes Nate a social pariah at school. Only the promise of winning the science fair holds any hope of happiness for Nate. He's building a cloud chamber, the project that he and his dad dreamed of working on together. Maybe if he can build it, Nate can give his father something that will help him feel better and finally come home.