ACT I
Carroll Todd (Toddy to his friends) is tenuously employed as the resident performer at Henri Labisse's Left Bank gay club, Chez Lui, where he entertains a small but appreciative audience (Paris by Night).

A penniless soprano, Victoria Grant, enters Chez Lui to audition - unsuccessfully - for Labisse. When Toddy tries to help, Labisse fires him. Toddy befriends Victoria and takes her home; they become instant buddies and confidantes. Toddy wishes he were a woman, while Victoria believes that there are far more advantages to being a man (If I Were A Man).

Richard, Toddy's ex-boyfriend, arrives at the apartment unexpectedly to collect his things. Victoria, wearing Toddy's hat and pajamas, punches the insulting Richard and kicks him out. Toddy is astonished that Richard thought Victoria was a man. The Inspired Idea strikes Toddy: Victoria could indeed be a man - Europe's greatest female impersonator! Toddy dreams up Count Victor Grazinsky, a gay Polish aristocrat and Toddy's new lover (Trust Me!). Le Jazz Hot! introduces "Victor" to Paris cafe society. His show-stopping performance immediately makes him the toast of Gay Paree. The only doubter of Victor's authenticity is a dashing American businessman-cum-gangster figure, King Marchan, who is visiting Paris with his brassy girlfriend, Norma. King is convinced Victor is a woman, and invites Victor to tango with Norma to prove it (The Paris By Night Tango).

In a Parisian hotel, Norma finds King preoccupied and uninterested in romance. In the hotel room next door, Victoria bemoans to Toddy that in King she has finally found the man of her dreams, but despite her feelings she must continue to convince him that she is a man (Crazy World).

ACT II
Victor continues to take Paris audiences by storm (Attitude). King, confused beyond endurance, sends an infuriated Norma back to Chicago.

King broods about his feelings for Victor and his doubts about himself (King's Dilemma). Is it possible that he, King, is falling for a man? King, Victor and Toddy meet for dinner at Chez Lui - where Victor and Toddy are invited to sing (You and Me). Later, King and Victor share a moment outside the boisterous club and King finally learns the truth (Reprise: Paris By Night).

Victoria and King examine the potential problems that would arise if they were to be perceived publicly as two men. (Almost A Love Song).

Back in Chicago, Norma is performing in a night club (Chicago, Illinois). When she informs King's gangster partner, Sal Andretti, of the goings-on in Paris, Sal announces they're all going to Europe. Two weeks later, King and Victoria are still unhappy (Living in the Shadows). Can Victoria stand to be a man anymore?

Sal, the spurned Norma and Chicago's underworld arrive in Paris, hoping to trap King in a compromising situation. Meanwhile, rival club owners are trying doggedly to unmask Toddy's new star. Comedy and confusion abound in a madcap, mistaken-identity-melee. At the nightclub that evening, the curtain rises on Victor's act and everyone waits for an answer - is it a She who's a He or a He who's a She?