Mrs. Kane is about to have a baby. Harry knows the baby will be a boy. He has his own special scientific theory to prove it. He already has two older sisters, Chloe and Dorthy and that's enough. Another girl would make the family lopsided. Harry's theory proves to be correct. The baby, Arney, is a boy.
But Harry's scientific theories aren't always successful. Guess what happens when he decides to make compost for his mother's houseplants? And even his best idea, the B.O.N.G. (Boys Only, No Girls) Club, doesn't work out exactly as he wanted.