The story revolves around the Andersons, a wealthy and wacky family who resides in Los Angeles, California. Everything is turned upside down when a strange boy named Jonathan arrives and claims to be an illegitimate son of Wilfred, the wimpy father of the family. That turns out not to be true, but aside from his trickery, the kind nature of the child conquers all the members of the family, who decide to adopt him, along with his dog Adam.