The Willoughby parents, incompatible with their station in life and rather forgetfully irresponsible, attempt to dispose of their children with benevolent or malevolent endings for the appropriate parties.
The four Willoughby children have somewhat learned to occupy themselves without their parents' input. The eldest, Tim, has quite learned to boss his twin brothers (Barnaby A & Barnaby B) and especially his younger sister Jane (who is not particularly allowed to have her own opinion). When a baby is left on their porch and their mother doesn't want it (she doesn't want any of her children, really), Tim names her Ruth and the children put her on the steps of a local millionaire, Commander Melanoff. (He earned his fortune by inventing a popular candy bar.) He has been quite depressed since his wife left him (he thinks that she and their son are dead), and the baby turns out to be just what he needs to turn his life around. He begins to pamper her and clean out his house, unaware that his ex-wife and son are not dead as he thought, but quite alive in Switzerland.
At the Willoughby's, meanwhile, When the their parents go on “vacation” and their dear Nanny comes into their lives, they are perfectly happy with the former, but not with the later – at first. She whips them into shape, teaching them to eat their oatmeal without complaining, respect her and each other, and even to like her. They follow their seemingly reckless parents' letters, though they do not die, to the chagrin of their children.
Then their house goes on sale. Their nanny helps them act as parts of the house / furniture and scare people away. This works for a while. When the house is finally sold, after rejecting a number of Tim's romantic and old-fashioned ideas on what to do, the Nanny arranges to have them live with Commander Melanoff, who is instantly impressed by her.
Melanoff's son, meanwhile, off in Switzerland, is sent off hiking by his mother and her new husband, the punctilious postmaster, to improve character. He is sent alone. He is miserable in Switzerland; he cannot stand the absolute precision of everything there, and he misses his father, and German is so incredibly difficult for him. He decides to search for his father instead, with a wrapper from the Melanoff candy factory to guide him. At about this time, the parents of Tim, Barnaby A & B, and Jane hike into the Swiss Alps in summer clothers and freeze to death.
Back in America, Melanoff, inspired by his little baby girl, Ruth, has invented a candy bar named Little Ruthie. Jane has read through his letters, not totally understanding them, and by talking about them at dinner, makes Commander Melanoff realize that his ex-wife and child are still alive. Melanoff is seized with regret over his son when his son rings the doorbell. Melanoff's son is also named Barnaby, so Barnaby A and Barnaby B are promtly renamed (according to their own preferences) Bill and Joe.
The Little Ruthie candy bar is a flop, but no matter. Melanoff and Nanny get married and take their six children to Switzerland every summer to hike. Ruthie grows up to marry Tim, who becomes an attourney. Bill and Joe run a clothing store. And Jane grows up to be a feminist with three daughers with long names – quite befitting of her character.
Best part of story, including ending:
Lowry's book is humorously written and she quite often references other well-known children's stories as references when they are discussing their problems or how to proceed.
Best scene in story:
When Melanoff finds Ruth on his doorstep, and he comes out of his daze, he begins to think and care about someone other than himself. He begins ordering things for her, asking the salespeople for advice, and seeing the old pizza boxes and other rubbish around his mansion for what it is.
Opinion about the main character:
All four Willoughby children are amusing and want to be good. They are most certainly better than their parents. Yet all have faults and / or problems to be solved (and they are successfully solved). The eldest, Tim, is in the habit of ordering around his siblings in a misinformed fashion (though his intentions are good), though the Nanny takes care of this. The twins have the same name, but are renamed with quite satisfactory names at the end. And Jane, as the youngest, isn't heard quite often enough, though is able to establish herself and her identity as time goes on.