Hank Whirling needs a bank loan to keep his Whirling Circus going. He gets it from a stuffy New York City bank, but only on the condition he take along accountant Randy Sherman and publicist Helen Harrison to help the circus turn a profit.
Hank's top act is the Colino trapeze troupe, featuring family patriarch Zach Colino and newcomer Tommy Gordon, as well as ringmaster Hans and clown Skeeter. Unknown to Hank, his little sister Jeannie has held a lifelong ambition to fly on the trapeze and has been secretly training with the Colino act for the past year.
An unknown saboteur sets a lion loose at a party thrown to celebrate the start of the circus season, terrifying the VIPs in attendance until Hank manages to capture it with the help of Colino. Helen accuses him of staging the incident for publicity. Subsequently, they discover the lion's cage had been deliberately opened.
Harrison and Sherman are infuriated by Whirling's refusal to accept their help. Hank and Helen clash over the best way to publicize the show; he feels she is intruding on his turf because he actually IS a very good publicist. Hank and Randy get into it over Randy's economizing on payroll by firing 40 roustabouts and replacing them with a stake-driving machine that expedites raising the Big Top. The stake driver is sabotaged and sets one of the show's hay piles afire; only swift action by Hank keeps the main top from catching fire. Hank, Helen and Randy begin to wonder if a saboteur is riding with the show.
The first section of the circus train, the unit with most of the performers aboard, derails en route to a new stand. Mama Colino, the show's "den mother," is killed and Zach Colino is heartbroken. He loses his nerve and is unable to go on. As he is the star of the show and the show's publicity is built around him, this is a major disaster for the Whirling Circus. Coupled with the foul weather they have been enduring for weeks that keeps the circusgoers at home, the books are looking grim. Only glib talk by Sherman keeps the show on the road.
Hank conceives a bold scheme. He will scrap the route he had laid out, do one show in Buffalo, New York and then slip into New York City three weeks before the Borman Brothers Circus, from whom the Whirling show had broken away, play the Big Apple, and cut the circus crowd right out from under them. But to make his plan work, Whirling needs a major publicity splash. Helen proposes a stunt last performed in the 19th Century: walking across the gorge at Niagara Falls. Hank goads Zach into making the wire-walk by calling him a coward. Colino swears that first he will walk the Falls, and then he will personally kill Hank. But on successfully completing one of the most dangerous wire walks in history, Zach realizes Hank said what he said only to help him, and they reconcile.
With the bank about to foreclose, Hank goes to television star Steve Allen to seek needed publicity for the circus. Allen buys the rights to broadcast the opening night performance in New York City for enough money to pay off the show's line of credit and enable it to move ahead with proper capitalization. When the NYPD arrives on the lot looking for Tommy, the Colino Troupe's catcher, and inform the show's management that Tommy is an escaped lunatic, Hank realizes that Tommy is the culprit behind the sabotage and Mama Colino's death.
Jeannie Whirling's debut with the Colino Troupe almost becomes a final performance when Tommy deliberately misses a catch, but Jeannie saves herself by grabbing onto one of the climbing ropes. Tommy tries to flee from Zach Colino, out to avenge his wife's death, and takes a fatal fall from the rigging. Down below, Hank and Helen realize what has been obvious to everyone else on the show: that they are in love with each other. The movie ends with Hank Whirling and Helen Harrison passionately kissing on one of the floats used in the spectacular finale of each performance as it parades around the track of the Big Top.
- Victor Mature as Henry Jasper 'Hank' Whirling
- Red Buttons as Randy Sherman
- Rhonda Fleming as Helen Harrison
- Kathryn Grant as Jeannie Whirling
- Vincent Price as Hans Hagenfeld
- Gilbert Roland as Zach Colino
- Peter Lorre as Skeeter
- David Nelson as Tommy Gordon
- Adele Mara as Maria 'Mama' Colino
- Howard McNear as Mr. Lomax
- Charles Watts as Jonathan Nelson
- Steve Allen as himself (cameo)
Famed circus performer Barbette served on the film as a consultant.