From 1831 to 1836, Victor Hugo and Louise Bertin collaborated on an opera titled La Esmeralda. For Hugo, it would be the only opera libretto he would ever write, a mere footnote to his collection of widely admired novels, plays, and poetry; for Bertin, however, it would become her most important work, yet seemingly destined to fade into obscurity like so many great pieces of art. Using Schenkerian analysis, this thesis uncovers the tonal and voice-leading structure of the first act of La Esmeralda. A study of this nature, which operates from the premise that forms as large and complex as opera can be examined in terms of a large-scale structure, is valuable because it sheds new light on the correlation of tonal structure and dramatic organization. Through these methods, Act I of La Esmeralda is read as a background progression from D major (with F# kopfton) to F major, composing-out an F#/F♮ dichotomy introduced in the overture. With reference to several musical-symbolic ideas - including the representation of virtue through the pitch F#, the key of Notre-dame's bells - it is shown how the musical structure of Act I expresses the Hugolian themes of fate and decay.