This was not the first talking picture of any of the three leads - Jean Arthur, Buddy Rogers, or Paul Lukas, so they had some experience with the medium. Still apparently direction and diction coaches did not get in the way either and as a result the three give very natural performances. For that matter, the entire cast is good. I'm spoiling this one almost completely, so if you don't want the details, do not read on.
This film is centered on a young circus acrobat, Greta (Jean Arthur), who cannot seem to get the other lead acrobat, Nick (Paul Lukas), out of her hair. He seems to think she belongs to him, and when he finds out she took a simple walk with the other acrobat, the guy has "a little accident" and falls to his death during their next performance. Nick claims the other acrobat was clumsy and just fell, and that he tried to grab hold of his hands in the act, but he just could not hold on. Everyone buys this claim, including law enforcement apparently, and Nick is still employed with the troupe. Then, when Nick tries to force Greta into another embrace on the train, Greta sees the scratch marks on Nick's wrist - scratch marks that point to the dead acrobat desperately trying to grasp Nick, but Nick letting go anyways.
So now Greta knows Nick is a murderer. Does she tell law enforcement or the head of the circus while the evidence is still fresh on Nick's wrists? No! She just gets off the train at the next stop, not even knowing where she is and with no plan and intentionally misses her train when it leaves, with all of her luggage still on it! Now Greta is intent on not going back to the circus until she finds out that a guy she fell in love with in the small town (Buddy Rogers as Ned) has left that town to be an acrobat in her old show. Forget that Greta's old troupe was a first class troupe and Ned's only experience is working on crude equipment in his barn (why would this top of the line troupe hire a newby?), Greta going back to the circus after not outing a murderer inspired by his jealousy is going to possibly precipitate another "accident", since she and Ned actually are in love, murderers (Nick) don't tend to be redeemable characters, and the fact that Ned and Nick are going to be acrobats gives Nick a perfect opportunity again.
The ending is preposterous. After Nick has been relentless in his pursuit of Greta, after another murder attempt in mid air is thwarted by Ned's resourcefulness, the solution to the problem is as simple as Ned beating up Nick and telling him to get his things and not come back! The end! It's like an old western where the good guy tells the bad guy "this town (circus) ain't big enough for the two of us pardner!" and the bad guy just runs. In other words, they make Nick out just to be another cowardly bully who only needs to be stood up to. Forget that he has already gotten away with murder.
The strongest performer here is Buddy Rogers who shows great energy and likability. I guess if Jean Arthur didn't have such a great future as a screwball comedienne I'd think more of her performance, but she plays such a mouse here. Lukas is great as the sociopath romantic. Helen Ware adds some needed levity as the fake mystic of the circus. She's great and that's odd since she usually did dramatic roles. Oscar Apfel, a man who changed careers from silent director to sound era character actor, is good in a bad part - the most passive circus manager of all times, ignoring obvious inter-employee harassment and possible homicides all around him. Charleton Heston of "The Greatest Show on Earth" he is not. Then there is Edna West as Ned's mother. I guess the film couldn't have two aggressive characters trying to thwart young love and young plans, but her character comes off as a bit too passive. Her son wants a career flying about in the air as an acrobat without a net - she says "fine". Her son falls in love with a stranger about whom she knows nothing in just two days and she says "fine". Just too good to be true. If this was today and not 1929 I'd say "Put down the Paxil Mrs. Lee".
I'd say if you are a film history buff, then this is a 7/10 just for the goofiness of it all. If you are not a film history buff, it is probably just going to be mediocre for you, a definite 5/10.