Act One

It is the turn of the twentieth century in New York City's infamous Tenderloin district, where everyone's livelihood depends on an economy of sin. The rich men pay the call girls. The call girls pay off the police. The police are in cahoots with Tommy Howatt, a slick and ambitious young reporter who will do anything to climb the ladder of success. But there's one person who threatens to ruin it for everyone: the pious Reverend Brock, whose fervent crusade to shut down the Tenderloin has ignited a furor from the district's resident sinners. Nita and her fellow call girls, in particular, can't understand why this Reverend Brock can't just mind his own business and let everyone else mind theirs ("Little Old New York").

Tommy Howatt comes out of a Parish House arguing with Jessica, the Parish clerk. She has denied him an interview with the Reverend. Along comes the beautiful society girl, Laura Crosbie, followed by her elegant young suitor, Ellington Dupont Smythe, the Second. When Tommy learns that Laura is a member of the church choir, he dupes Jessica into letting him enter the church by telling her that he would also like to sing in the choir.

Inside of the Parish House, Laura's Uncle Purdy, an elderly, well-dressed businessman, sits with the nouveau-riche country bumpkin, Joe Kovack, who's recently found coal on his farmland. Rev. Brock enters, and the two men hesitantly tell him that some of his parishioners don't agree with his attack on the Tenderloin. Martin, the choirmaster, joins them to deliver a similar plea on behalf of the ladies auxiliary, who would like Brock to give more traditional sermons. The men leave, and Brock sits alone, frustrated that his church wishes to remain ignorant of the sin that surrounds them. He resolves that he must continue his crusade full force – every day of the week ("Dr. Brock").

Jessica escorts Tommy into the church. She goes to find Martin, leaving Tommy alone with Laura. He tries to schmooze her into getting him an interview with Brock, finding himself attracted to her. Copying Ellington, he introduces himself as Thomas Howatt... the Second. She's on to his ploys, but seems a bit charmed in spite of herself. Jessica enters with Martin, who sizes up Tommy and determines that he's not fit for the church choir. Tommy, who makes some cash by singing in a club in the Tenderloin, gets an idea. He opens the door to Brock's office the tiniest bit and lures Brock out with his fantastic singing ("Artificial Flowers"). Brock calls for Martin and orders him to use Tommy in the choir. Tommy tells Brock that he heard his inspiring sermon last week and would like to help him with his cause by informing him about the goings-on to which he's privy, from his job as a reporter at The Tatler. Although they're each suspicious of the other, they share a certain stealthy ambition ("What's in It for You?").

At the Nineteenth Precinct Police Station, Tommy waits to speak to Lieutenant Schmidt. The Precinct is full of a rag-tag group of prostitutes and drunks. Tommy warns Schmidt that Reverend Brock is on his way to the police station to have it out with him. It seems as though Tommy is something of a double-agent. The Sergeant spots Rev. Brock outside, hitching up his horse, and pandemonium erupts as Schmidt orders all of the derelicts out of the room. By the time Rev. Brock enters, all is quiet, and Schmidt feigns surprise at Brock's visit. Brock reports lascivious behavior at Spanish Anna's, one of the Tenderloin's most active bordellos, suggesting that Schmidt and his men investigate. Schmidt pulls the wool over Brock's eyes, insisting that he's never heard of such a thing going on in his precinct and promising to come down hard on any immoral behavior. Brock exits, and Tommy comes back in, having proven himself of great worth to the Lieutenant. Gertie, a young prostitute, and a couple of her friends spot Rev. Brock on the street. The girls mock his useless attempts to change the Tenderloin ("Reform").

On the other side of town, Laura and Jessica sit in the parlor of Laura's posh Fifth-Avenue home. Jessica reads aloud to Laura about Lieutenant Schmidt's raid on Spanish Anna's. Purdy enters, disgusted that the girls are bothering themselves with such filth. He's disgusted by Brock's campaign against sin and all of the lowlives that it seems to be stirring up and bringing out into the open. He's particularly disgusted with Tommy Howatt. Laura protests, insisting that Tommy is not the ruffian that her uncles believe him to be. She informs him that she has invited Tommy over that very afternoon. When Tommy arrives, Jessica goes to fetch some tea, leaving Laura alone with Tommy's exaggerated stories and obvious advances. Laura finally blows a fuse when Tommy reads to her a poem by Lord Byron that he claims to have written himself... just for her. Laura pleads for him just to be himself, but when Tommy leaves, Laura recognizes that she is not being herself, either; her calm is a façade to hide the growing excitement that she feels for this crude young gent ("Tommy, Tommy").

That evening at Clark's tavern, Detective Frye conducts a horse race with two prostitutes mounted on the shoulders of two male customers. The rest of the rowdy patrons look on, laughing and cheering. Joe Kovack enters nervously but befriends Nita with a twenty-dollar bill. The two sit and chat over champagne. Tommy walks, in late for his call, and goes right up onstage to sing a number for the bar ("The Picture of Happiness"). Joe recognizes Tommy from singing at the church. Nita thinks this is a hoot and shoos Joe away to find out what Tommy is up to. Old, gentle Joe protests; it appears that he's very quickly become attached to Nita, but she tells him to get lost, pushing him into a booth with Gertie. Tommy tells Nita all about how he's double-crossing both the police and Rev. Brock. Later that night, a very drunk Joe Kovack is escorted out of Clark's by a cop.

Early the next afternoon, Purdy sits on a beach dourly reading The Wall Street Journal as his niece, Laura, enjoys the sun with Jessica and some girlfriends. Purdy begin to argue with Brock about the Tenderloin, but Brock cuts him off, insisting that it's much too nice of a day to bother themselves with their differences ("Dear Friend"). Tommy joins the group, and he and Laura spend some time taking pictures of each other and wrestling playfully. Joe then enters, distraught. He admits to his night out and his subsequent trip to jail. He also tells Brock that he overheard some guys in jail talking about how Lieutenant Schmidt had fooled Brock with a fake raid on Spanish Anna's bordello. Brock confirms the story with Tommy. With a new resolve to take down the Tenderloin, Brock enlists Tommy and a group of stalwart young men to join his now explosively fanatical crusade. He plans to infiltrate the houses of ill repute disguised as patrons and collect evidence. He will then give the evidence to state and city officials, who will have no choice but to close down the Tenderloin for good. With God on his side, Brock rallies the spirits of his men ("The Army of the Just").

That night at Clark's, the usual party rages on. Joe enters and approaches Nita. He admits that he's fallen in love with her. However, he knows better than to get mixed up with a woman who makes her living by giving men "special attention." He's planning to go away for awhile, until he gets over it, but not before he can give her a small present. Nita opens the package to reveal a huge diamond ring. Joe tells her that he has recently become a millionaire. His thinking is: if she ever gets into a jam, she can sell the ring. He begins to bid her farewell, but she asks him to come back to see her tomorrow. Joe sees Brock and his men enter Clark's and shimmies out on his hands and knees to avoid being spotted.

Brock and his army make their way around the joint, pretending to be customers; they take notes on the depravity that they're witnessing. One thing leads to another, and Brock finds himself in a wild game of leapfrog with a group of women. He takes notes all the while. Nita is still aglow from scoring a millionaire. She and the group reflect on how easily money changes hands in the Tenderloin ("Money Changes Hands"). At the end of the night, Brock and his crew have enough evidence to take down the Tenderloin.

Act Two

A few days later, Purdy wanders through Central Park, searching for Laura, when he happens upon Joe, who is dejected by his impossible love for Nita. Brock and Martin, in the midst of a grave conversation, approach. They stop to discuss the details of Brock's latest sermon denouncing the Tenderloin in light of the raucous behavior that they witnessed at Clark's. Mrs. Barker, an older church lady, invites Brock to join her group of friends for a game of spoons, but he refrains. Just then, Jessica runs in, breathless – Lieutenant Schmidt is looking for Brock. She's concerned that something bad is about to happen, but Brock takes this to mean that the Governor has taken action on the Tenderloin, and the cops have come to beg for mercy. Delighted, he takes Mrs. Barker up on her offer, after all ("Good Clean Fun").

Tommy and Laura enter the park together. Laura reveals that her uncle believes that Tommy makes his money by gambling. Obliged to conceal his true source of income, Tommy pretends that he is, in fact, a gambler and that he always wins on account of a lucky picture that he keeps of Rev. Brock. Purdy wants Laura to stop seeing Tommy, but she refuses. Tommy's levity, whether of truth or fabrication, seems to lift her spirits, and Tommy takes her in his arms to dance ("My Miss Mary").

Meanwhile, Schmidt arrives to confront Brock about his crusade. Schmidt tells Brock that he doesn't like the bordellos any more than Brock does, but he's reconciled that the sin in the city is what keeps both him and Brock in business. Schmidt argues that shutting down the Tenderloin won't clear the city of sin. Meanwhile, Brock has alienated his congregation, and Schmidt faces losing his job. Schmidt becomes infuriated when Brock won't listen.

At Clark's, the girls lament the loss of business. Nita scoffs at Gertie for dreaming of finding love, but inside, she laments losing Joe ("My Gentle Young Johnny"). Just then, Joe enters. He tries to pay, but Nita refuses the money, telling Joe how she's missed him. Impulsively, Joe asks Nita to marry him, and when she accepts, the girls erupt in a giddy celebration ("The Picture of Happiness – Reprise"). Tommy arrives, and Schmidt asks him about his lucky picture of Rev. Brock. As Schmidt and Deacon examine the picture, it's clear that they have a scheme brewing.

Days later, Jessica, Laura, Joe and Purdy find themselves reading scandalous news of Rev. Brock philandering in the Tenderloin – the proof is a doctored photo of him with two women ("The Trial"). That night, Clark's is ablaze with celebration as Frye gives the girls the perfect imitation of Brock and his failed crusade. Meanwhile, at the Parish House, Brock sits alone, solemnly reading The Bible. Tommy comes in to apologize for the way that things have turned out. Regardless of Brock's impractical idealism, Tommy has come to value the Reverend. As Brock insists that he still believes that people are fundamentally good, Tommy rushes out in a swell of guilt for giving Schmidt the photograph.

Back in court the next day, Brock sits on trial as the chairman interrogates him about the picture. Finally, Tommy stands up and admits that the picture is fake. Schmidt roars at him, but Tommy presses on, exposing the entire truth. Brock is satisfied that Schmidt's evil-doing will at last close the Tenderloin.

Schmidt and Frye patrol a dead-quiet street. They've got a hitman looking for Tommy, because all of the establishments of the Tenderloin have closed and all of their business has dried up. Schmidt is sickened by the sight of a group of girls with their bags packed. They're heading west to find work elsewhere – they assume that they shouldn't have any trouble; all men are depraved ("Little Old New York – Reprise").

Vindicated, Brock relaxes at the Parish house with Laura, Jessica and Joe. Purdy comes in with news from the Church Elders. It appears that although they appreciate Brock's determination and regret the scandal that he endured, they feel that all of the turmoil has destroyed the character of their church. They ask him to step down. Brock, now an exile, stands in shock as Tommy, likewise an exile, enters to wish Laura farewell. He is going to start over in Denver ("Tommy, Tommy – Reprise"). Tommy bids Brock goodbye, and the Revered thanks the young man for giving him back his name.

In Detroit, Brock addresses his new congregation. He has already begun to plot a new crusade against sin. This place is no different from the Tenderloin, and as Brock continues with his tirade, he is slowly drowned out by the sounds of prostitutes, bums, liquor, dancing, cops, ambitious journalists and zealous old preachers colluding in a new, but strangely familiar refrain ("Little Old Detroit").