The novel's central character is Étienne Lantier, previously seen in L'Assommoir (1877), and originally to have been the central character in Zola's "murder on the trains" thriller La Bête humaine (1890) before the overwhelmingly positive reaction to Germinal persuaded him otherwise.
Étienne is portrayed as a hard-working idealist but also a naïve youth; Zola's genetic theories come into play as Étienne is presumed to have inherited his Macquart ancestors' traits of hotheaded impulsiveness and an addictive personality capable of exploding into rage under the influence of drink or strong passions.