The swallow saved, the boy abandoned
As a young boy, Riccetto dives into the Tiber to rescue a drowning swallow. Years later, now older and hardened by hustling and a spell in prison, he watches the younger boy Genesio drown in the Aniene. He does nothing, then walks away so he won't be implicated. The two river scenes frame the novel and show slum life gradually replacing a spontaneous impulse to help with self-protective indifference.