"Los Tres Huastecos" is an old fashioned comedy/musical/adventure film. In many ways, it's similar to the Hollywood musicals of the period and is a good introduction to Mexican cinema for non- Mexicans.
The story begins with a prologue. You learn that there were three identical brothers who were sent to live in three different homes when they were orphaned. Because they grew up apart, the boys followed very different paths. One became a conservative priest, one a roguish policeman and the other a disreputable sort who people think might be a murderous bandit. When the film then begins, the policeman has been sent to capture the bandit, the priest has been assigned to a new parish and the third brother happens to live in this same town. What's next? See the film.
What I loved about this film is the great cinematography. While today we take camera tricks for granted since they are so much easier to do in this computer age, back then you needed an extremely talented cameraman and an equally talented director to make a film with one actor playing three different parts--which Pedro Infante does here. Yet, amazingly, this is done seamlessly--even in scenes with two or three of the brothers! And, of course, Infante must be praised for doing a wonderful job with such different characters.
As for the movie itself, it's fun but also a bit dated. In particular, the music is a bit poor--with a real canned sound to it. I've noticed this in many musicals from abroad, as getting the sound right in musicals is something Americans take for granted, as after about 1932, the Hollywood musicals achieved this. But, here it just sounds like someone is playing a record or singing in a tiny room-- and it sounds odd. But this really doesn't take away from the rest of the film that much--it still is fun and quite enjoyable to watch.