Joe Bascomb (Lou Costello) chases con man Harry Lambert (Bud Abbott) to Mexico City, after Harry apparently swindled him (and some friends) in an oil stock scam back in the United States. Joe's ex-girlfriend, Mary (Virginia Grey) has hired Harry as her agent, and is going by the name 'Montana', passing herself off as a toreador. When Joe encounters Harry at a bullring arena, he also sees Mary, who is in the ring. As part of 'Amigo Americana Week', she is about to toss her hat into the crowd where the lucky recipient will be proclaimed 'goodwill ambassador'. Mary is supposed to toss the hat to Gus Adamson (Frank Fenton (actor)), another con man whom Harry has arranged to be chosen, but Mary instead throws the hat in anger at Joe. It turns out that Joe, now the 'goodwill ambassador', is also being pursued by American authorities for partaking in the oil stock scam; he uses an alias, 'Humphrey Fish', while in Mexico.