The outside of the theatre marquee is lit, advertising: "Pretty Lady Gala Premiere." The orchestra begins its overture as chorines scramble downstairs to their places. Dorothy has been with Peggy in her dressing room during the preparations, and with a trembling, teary-faced look, gives her final words of benediction:

You look adorable. Now go out there and be so swell that you'll make me hate you.

The curtain rises on Pretty Lady. Southern belle chorus dancers kick out onto the stage in a line. Backstage, Marsh is nervously pacing. When Sawyer is brought out of her dressing room, Marsh delivers immortal lines (a show business cliche) to his terrified, open-mouthed chorus girl just before she goes onstage - his last-minute instructions:

Sawyer, you listen to me and you listen hard. Two hundred people, two hundred jobs, two hundred thousand dollars, five weeks of grind and blood and sweat depend upon you. It's the lives of all these people who have worked with you. You've got to go on, and you have to give and give and give. They've got to like you, they've got to. Do you understand? You can't fall down. You can't, because your future's in it, my future and everything all of us have is staked on you. All right now, I'm through. But you keep your feet on the ground and your head on those shoulders of yours and go out - and Sawyer, you're going out a youngster, but you've got to come back a star.

Peggy is pushed on-stage and greeted by cheers from the Southern belles. She delivers her insufferable line of dialogue, still somewhat flatly: "Why Jim, they didn't tell me you were here. It was grand of you to come." The train conductor announces: "All Aboard, the Niagara Limited."

The film ends with three, full-scale production numbers (choreographed by Busby Berkeley), part of Julian Marsh's show:

• Shuffle Off to Buffalo
• I'm Young and Healthy
• 42nd Street

Shuffle Off to Buffalo

After the conductor announces that the Niagara Limited is in the station bound for the popular honeymoon destination, the newly-wed couple (Peggy and an unnamed groom (Clarence Nordstrom)) eagerly leave for their honeymoon from the train platform and are waved good-bye by their friends. Jim pins a "Just Married" sign on the "Shuffle Off to Buffalo" groom's back. Aboard the honeymoon express on the back of the caboose, Peggy and her beau sing the title song cheek-to-cheek, a serenade which contains slightly ribald lyrics:

...The honeymoon in store
Is one that you'll adore
I'm gonna take you for a ride
I'll go home and pack my panties
You go home and get your scanties
And away we'll go
Off we're gonna shuffle
Shuffle Off to Buffalo
To Niagara in a sleeper
There's no honeymoon that's cheaper
And the train goes slow
Off we're gonna shuffle
Shuffle Off to Buffalo...
For a little silver quarter
We can have the Pullman porter
Turn the lights down low
Off we're gonna shuffle
Shuffle Off to Buffalo

Quite dramatically, the caboose splits (jack-knifes) down the middle and opens up to reveal a cross-section of the whole length of the coach - many compartments or berths abruptly appear. The camera tracks back from the stage, including the orchestra pit and the applauding audience in its wide-frame perspective. After initially being kept apart by the dividing car, the honeymooning couple skip, slide, and dance down the entire length of the coach. Behind them in the compartments, an assortment of passengers point and laugh at them, making cynical fun of the honeymooners. Ann and Lorraine, two of the chorus girls, both wearing silky satin pajamas/nightgowns, are perched up in one of the upper berths. As they eat the two symbolic fruits of knowledge (an apple and a banana), they sarcastically sing about the inherent dangers of marriage:

Matrimony is baloney
She'll be wanting alimony
In a year of so
Still they go and shuffle
Shuffle Off to Buffalo
When she knows as much as we know
She'll be on her way to Reno
While he still has dough
She'll give him the Shuffle
When they're back from Buffalo

Now in their own sleeping garb, Sawyer and her partner do a shuffle/softshoe dance in front of the other berths, and then sit down in their own compartment and pull the curtain. With knowing glances, chorines grouped in pairs in the sleeping compartments close their curtains. Ann and Lorraine also appear in curlers and cold-cream as if to emphasize a shy bachelor's fear of marriage. Toward the end of the number, the Pullman porter prances down the corridor to collect the chorus girls' shoes to shine. Sawyer loses her innocence when she extends her arm with her shoes to be cleaned. She squeals with delight from a symbolic defloration by her husband - her arm suddenly rises in climax and then slowly falls. She drops her shoes to the floor and her arm goes limp. The black porter falls asleep as he polishes the shoes.

I'm Young and Healthy

In a white-coat tuxedo, Billy leaps onto the front of the stage and sings the lyrics to the song in front of a darkened curtain:

Say I know a bundle of humanity
She's about so high
And I'm being driven to insanity
When she passes by
She's a snooty little cutie
She's been so hard to kiss
I'll try to overcome her vanity
And then I'll tell her this

During the chorus, he moves over to serenade the young, forever-smiling, healthy, bleached blonde (Toby Wing) who reclines on a garden bench. The blonde reclines in a white, ermine-trimmed lower gown and ermine-bra (with bare midriff) while holding an ermine muff - her shoulders are deliciously bare:

...I'm young and healthy
And you've got charms
It really is a sin
Not to have you in
My arms
I'm young and healthy
And so are you
When the moon is in the sky
Tell me what am I
To do...

As Billy serenades the cheerful-faced blonde (who never utters a word but listens approvingly), the bench descends into the stage, and the camera angle shifts to high-angle shots of the couple on a dark, circular revolving turntable. As he cradles her in his arms, they are ringed by white-coat tuxedoed chorus boys who lie flat on their stomachs facing them and rhythmically move their heads back and forth. They all rise and two-by-two, the blonde is escorted into the front of a revolving line-up of other veiled blondes in similarly-brief, ermine-fur costumes who circle around the stage. When all the scantily-clad chorus girls have rotated around the invisible turntable, the blonde steps off the moving stage into Billy's arms for a prolonged kiss, filmed in close-up.

When they break from their kiss, the single-file line of endlessly-reproduced chorus girls appears between their lips and prances toward them. The line of identically-dressed blondes in their brief costumes form a round pattern and encircle the stage, joining arms and facing outwards. They all jump in tandem to spread their legs apart and the black reflective surface they stand on begins to rotate. The camera slowly moves forward to view the passing succession of shapely thighs of the synthesized chorines. Chorus boys emerge outside the ring of chorines, chase some of the women, and grab their waists. In three rings which are formed, the dancers engage in some trucking (running without moving) gestures and then break into smaller lines of four dancers each on three revolving pedestal/turntables.

Groups of four women (with their hands inserted in their white muffs) run toward the camera, sit, and begin swaying their knees back and forth. An overhead shot reveals two large circles of many more chorines who now form a fantastic kaleidoscopic pattern of motion - one of Berkeley's trademark "top shots." When the circular pattern breaks and the camera returns to a high-angle shot, the chorus girls grab long ribbons of fabric and pull them from the outer perimeter of the turntable toward the center. The ribbons are held and alternated from left to right. Another straight-down camera angle captures the pattern as a camera iris. The dancing ends with a spectacular thrusting shot of the phallic-like camera moving forward down a tunnel formed between the spread legs of the chorus girls who stand on the revolving stage - an example of the unabashed eroticism that Berkeley was famous for. At the end of the corridor are the smiling faces of Billy and the blonde.

Backstage, Annie is overjoyed with Peggy's "hit" success and she shares her pleasure with Abner, who sits dumbfounded with her dog in his arms. Abner is reminded to walk the dog - thereby keeping him absent from the grand finale of the film - the title song.

42nd Street

Smiling broadly, Peggy appears center stage from behind the curtain. She wears a white skirt slit up the length of its side, a white derby, and a puffy-shouldered dress. There in front of the curtain, she starts the number by simply singing the title song "42nd Street":

In the heart of little ol' New York
You'll find a thoroughfare
It's the part of little ol' New York
That runs into Times Square
A crazy quilt
That 'Wall Street Jack' built
If you've got a little time to spare
I'd like to take you there

Come and meet those dancing feet
On the avenue I'm takin' you to
Forty-second Street
Hear the beat of dancing feet
It's the song I love the melody of
Forty-second Street...

CHORUS:
Little 'nifties' from the Fifties
Innocent and sweet
Sexy ladies from the Eighties
Who are indiscreet - (Oh)
They're side by side, they're glorified
Where the underworld can meet the elite
(Naughty, gaudy, bawdy, sporty)
Forty-second Street

[Note: "Wall Street Jack" was possibly a reference to Jackie Kennedy's father, Wall Street stockbroker John Vernou Bouvier III, whose nickname was Black Jack. He had owned real estate around Times Square that his grandfather and father had developed. It was also rumored that the reference might be to John Pierpont "Jack" Morgan, Jr. (J.P. Morgan's son).]

The curtain parts behind her to reveal a backdrop of a street scene - New York's 42nd Street. She strips off and sheds her long slit skirt to do a heavy-footed solo tap dance. After a brief cut, the camera pulls back to reveal that she has been tap-dancing on the top of a taxi-cab which is caught in city traffic in the middle of New York's famous street. Peggy climbs down from the cab roof, hangs on to the inside of the open window, jumps on the running board, and is transported off-stage. The camera moves up the crowded street - at the corner of 42nd Street and Broadway - and captures the decadent, bustling night life of the area, pulsating to the beat. In front of stylized sets, the frantic, fast-paced activity of the residents on the street is magnified by the sheer amount of scenery and number of dancers.

Short, interwoven vignettes in a fast-moving, multi-leveled tap ballet present various, cartoonish, Broadway types along the way, all dancing to the same beat:

- a policeman twirls his stick
- an apple vendor juggles his fruit
- a tall sandwich-board man shuffles along
- a large black doorman trucks
- a very round woman walks her dog
- a barber works on a customer while dancing
- two patrons strut out of the barber shop
- numerous midgets walk out on the sidewalk
- a nursemaid spanks a doll baby's bottom in tune to the music
- two fruit vendors with a pushcart full of bananas hoist their golf bags on their shoulders to go play a game
- a newsboy holds a tabloid EXTRA in his arms
- a policeman allows the parading, dancing throng (and a man on horseback) to cross in front of automobiles
- two young, black street urchins tap-dance
- a cigar-store Indian chief comes to life
- a bystander doffs his hat outside the Enterprise Hotel building

The characters watch a sensationally-vulgar murder. After a girl's scream, the camera pans up to the upstairs window of the hotel where it witnesses a man suddenly bursting into a room. He angrily grabs and attacks the girl - but she kicks him back, knocking the light out. In terror, she clambers out the window onto the roof of the portico. Dozens of passers-by watch from the street level. When the man fires two shots after her, she does a swan dive into another man's arms on the street - there, she picks up the dancing beat with her rescuer, only to be stabbed in the back and murdered by the jealous pursuer who comes out of the hotel.

The camera does not linger on the street violence and her death - it pans back up to the open upstairs window of the next room over, where Billy drinks an illegal speak-easy concoction, mixed by a bartender behind him. He picks up the verse:

The big parade goes on for years
It's the rhapsody of laughter and tears
Naughty, bawdy, gaudy, sporty
Forty-second Street.

The camera pans down and across to closely-ordered, military-formation columns of chorus girls who tap dance along the street, each one dressed with a puffy-shouldered costume (identical to Peggy's dress). After swishes from side to side, male dancers join the girls, lifting some of them so they can kick their legs out. Long lines of chorus members, with their backs to the camera, mount multi-leveled steps of a giant platform at the back of the stage. When they all turn together, they hold out large, painted skycraper cut-outs, forming a rising, moving and surreal New York skyline.

Come and meet, those dancing feet
On the avenue I'm taking you to
Forty-second Street
Hear the beat of dancing feet
It's a song I love, the melody of
Forty-second Street

The buildings in the skyline separate, spreading apart and leaving a highway-striped stairway. From a different perspective, after a quick-cut edit, it resembles a flattened Empire State Building. The camera dollies up the stripe to the top of the skyscraper, where Billy and Peggy perch above the skyline, smile and wave to the audience. Before they embrace and kiss, they pull down an asbestos curtain (from somewhere above them) to conceal themselves. Now glorified as lovers and as a romantic couple, they are at the apex of their relationship - and commercial stardom. The Broadway play is a great success - Busby Berkeley's cinematic triumph over 'the Broadway stage' is dazzlingly realized as well. The escapist, upbeat production numbers in the finale contrast sharply with the harsh realities of the last brief scene.

Outside as patrons leave the theatre following the opening Philadelphia show, Marsh stands unrecognized with his trademark cigarette dangling from his lip. He is positioned at the lower end of the fire-escape that lets out patrons into a dark alley. The film ends on a grim, downbeat note - Marsh's life as stage director is over and he is too drained to even enjoy the opening's success. Yet he proved he could meet and triumph over subversive odds - with the effort and support of everyone's team work [in the Depression era, this was a powerful message].

Ironically, the taskmaster overhears some of the patrons saying that he is receiving accolades and taking unjustified credit for discovering Peggy as a new sensational star:

Oh, these directors make me sick. Take Marsh, he puts his name all over the program. Gets all the credit. If it wasn't for kids like Sawyer, he wouldn't have a show. If it's Sawyer's wish, she'll have Broadway in her pocket in a week...And Marsh will probably say he discovered her. Some guys get all the breaks.

Dorothy Brock's theme tune, "You're Getting to Be a Habit With Me" plays a few times as he wearily turns, flicks his cigarette away, and sits dejectedly on one of the lower rungs of the fire escape, in solitude.