Although Polly Adams was only seven when her mother left home, she immediately took responsibility for her younger brother, Jimmy. But she never forgave her mother, whom she had loved and trusted, for abandoning them.
When war broke out they were evacuated, with the school, to the Yorkshire Dales where Polly and Jimmy were taken in by the Braithwaites to live on their remote farm at the head of the dale. Here they were happy and secure and grew to love the Braithwaites, the farm and the lovely countryside around them, where they were free to roam and explore.
When they were, without reason, inexplicably removed from the farm and taken by Mrs Braithwaite to be billeted in the village instead, all Polly's old mistrust of the adult world was reinforced. Henceforward, she vowed, she would trust nobody, then nobody could let her down.
Determinedly hard and mistrustful, she spurns the efforts of those who are trying to help her. Responding to kindness with ingratitude, she becomes her own worst enemy. The Serpent's Tooth (the title taken from the lines in King Lear How Sharper than the Serpent's Tooth it is to have a thankless child) traces the damaging effect that those events of her childhood had on her adult life and how eventually Polly begins to understand the reasons behind both of those rejections, comes to terms with them and, freed of the burden of them, gets on with her own life.