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Louisa, Sam Pollit's eldest daughter by his dead first wife, decides the only way to save her younger siblings from their parents' war is to poison both Sam and her stepmother Henny with cyanide. When Louisa confesses, Sam refuses to believe her, and she leaves home to 'take a walk round the world.'
Sam showers his children with invented baby-talk, pet names, games and lectures, and this private language makes them an audience for his self-image rather than people with needs of their own. Because the affection is real in its warmth but serves the parent's ego, the child cannot name what is wrong without seeming ungrateful. The more he performs love, the less room anyone has to contradict him.
Sam believes in progress, science, the brotherhood of man and the perfecting of the race, and he uses those ideals to justify his domestic domination and to dismiss anyone who objects. The novel shows that a sincere belief in one's own goodness is what makes tyranny sustainable, because every complaint gets reframed as the complainer's moral failing. Watch for the person whose principles always happen to require others to defer to them.
Louisa grows up as the silent observer of a marriage of mutual loathing: Henny's debts and furious invective, and Sam's cheerful obliviousness. The novel argues that a child who sees clearly inside such a household cannot stay a spectator forever, because clear sight turns into responsibility for the younger children. Her maturation comes through rupture, a violent break from the family, rather than through reconciliation.