La Conquête de Plassans (1874) is the fourth novel in Émile Zola's twenty-volume series Les Rougon-Macquart. In many ways a sequel to the first novel in the cycle, La Fortune des Rougon (1871), this novel is again centred on the fictional Provençal town of Plassans and its plot revolves around a sinister cleric's attempt at political intrigue with disastrous consequences for some of the townsfolk.
At the start of the novel, the home life of Francois Mouret and his wife and cousin Marthe (née Rougon) is portrayed as a generally pleasant and relaxed existence. Francois is slightly compulsive in his behaviour and Marthe clearly suffers from some sort of mental illness, which Zola intended to portray as a genetic consequence of the Rougon-Macquart family's tangled ancestry. Their three children include the eldest son Octave, an intelligent but feckless ladies' man (featured as the principal character of two later novels in the cycle, Pot-Bouille (1882) and Au Bonheur des Dames (1883), but