Serge Battour, orphaned son of a French viscount and a Roma woman, endures significant discrimination due to his mixed heritage from both peers and family. This shapes his entry into Lacombrade Academy, his late father's alma mater, where he seeks acceptance and belonging. Fundamentally kind, idealistic, and morally principled, he is also a piano prodigy whose talent and perseverance allow him to maintain noble humanity despite ostracism, striving to connect through empathy.

His development centers on a tumultuous relationship with roommate Gilbert Cocteau. Initially facing hostility and manipulation when extending friendship, Serge's unwavering altruism gradually breaks Gilbert's defenses, forging a complex emotional bond that evolves into romance. This forces Serge to confront emerging homosexuality, causing confusion and distress. He finds little guidance or acceptance from institutional supports like the church or peers, intensifying his internal conflict against late 19th-century societal norms.

As their relationship deepens, Serge becomes Gilbert's emotional anchor, offering stability against Gilbert's self-destructive tendencies rooted in past trauma. Following collective rejection at Lacombrade, they flee to Paris. There, Serge witnesses Gilbert's psychological unraveling through drug use and prostitution. Despite Serge's support, Gilbert dies in a tragic accident, leaving Serge profoundly traumatized until friends later find and console him.

Serge transitions from an optimistic newcomer seeking acceptance to a figure irrevocably marked by love, trauma, and defying societal boundaries. His arc encapsulates the struggle between idealism and harsh reality, portraying resilience amid profound tragedy.