Tom Mix and his equine companion Tony the Wonder Horse had a solid career in Westerns, but just occasionally Mix (or his producers) made a commendable effort to vary the formula ... notably with 'Dick Turpin', in which Mix played the long-riding highwayman and male horse Tony played Turpin's mare Black Bess. 'The Circus Ace' is a more reliable variant on Mix's usual formula, basically the Mix as before ... but with elements of circus life brought in to vary the action and visuals.SLIGHT SPOILERS COMING. Tom Terry (Mix) is out on the range with Tony when a woman falls out of the sky, dressed in a spangled leotard. She's Millie Raleigh (Natalie Joyce), doing a parachute act for a travelling circus. (How can the audience appreciate the parachute act, if she lands miles away from the tent site?) Tom helps her get back to the circus, and he promptly gets 'with it' by joining the show, doing his trick riding and roping acts.When the circus reaches its next town, Millie rides an elephant in the circus parade up the high street. Tom's gunfire startles the elephant, who stampedes with Millie in tow. Tom gallops ahead on Tony, his lasso at the ready. I thought Mix was going to lasso the elephant, but he did something slightly more plausible.One of the men with the circus is named Kirk Mallory. With a monicker like that, you just know he's a villain. Sure enough, Mallory gets Tom framed on a false charge, and soon the sheriff has nicked Tom and hauled him off to the calaboose while the circus is about to leave without him. There's a funny but implausible scene here. The sheriff has conveniently allowed Tom to keep his jack-knife with him in his gaol cell. (Very hospitable!) The cell contains one of those prison-cliché beds that hang from chains on the wall, and a wooden chair. Tom nervously whittles the chair down to a pile of shavings. When he's given a broom and ordered to sweep up the shavings, he carries on shaving the broom handle. Of course, faithful Tony helps Tom bust out of prison. (Why didn't the sheriff arrest Tony too?)There are a couple of amusing sight gags with a kangaroo during the circus sequences. Natalie Joyce, tall and brunette, is not conventionally pretty but looks quite attractive in her circus tights, and she gives a splendid performance. I'll rate this movie 7 out of 10. Tom Mix's middle name was Collins. (Boom, boom!)