Tonio Rossi, elder brother to protagonist Marco Rossi, calls 19th-century Genoa home amid a family strained by financial hardship. Their father Pietro’s charity clinic, crumbling under the weight of debt, drives Tonio to uproot his life for Milan—a practical response to economic crisis, preceded by his mother Anna’s own journey to Argentina in search of work.

In Milan, Tonio finds work at a railway station, trading coastal breezes for steam and coal as he begins an apprenticeship as a locomotive driver. By night, he steals hours for self-study, juggling shifts and textbooks until his relentless drive earns him an engineering degree. His physical absence from Genoa leaves Marco feeling shut out of pivotal family choices, a rift that spurs Marco to embark on a solitary quest to reunite with their mother.

Tonio’s mischievous pet monkey Amedeo later accompanies Marco on this journey, serving as a living reminder of Tonio’s presence even in separation. Though Tonio’s story unfolds primarily beyond the main narrative’s focus, it remains anchored in the family’s financial battles and his scholarly triumphs. No documented extensions explore his story beyond these core events.