While dressing for a big concert, Brazilian singing star Marquita Romero (Movita) gets a shocking cable from a female stranger. Marquita's brother, Carlos, has been arrested for murder in New York and urgently needs help. Informing her suitor Steve Warren (Warren Hull) that she must leave Rio for New York at once, the distraught vocalist joins the mystery woman who turns out to be her sibling's bride.
Together the women try in vain to get the innocent man out of jail. Steve comes to the rescue and hires Mr. Montgomery, a big-time lawyer who thinks the real killer is a shifty nightclub owner known only as "Mitchell." To uncover the truth, Marquita gets a job singing in his club. Jealous, the proprietor's girlfriend, Vicki (Kay Linaker), schemes to get rid of her - imperiling Marquita and the last-ditch plan to save her brother.
Prior to her work on Girl from Rio, Movita (Castaneda) appeared in the great classic adventure, Mutiny on the Bounty (1935), starring Clark Gable and Charles Laughton.
One of the most popular serial movie actors of the 1930s, Warren Hull starred in several action serials, including The Spider's Web (1938), Mandrake the Magician (1939), and The Green Hornet Strikes Again (1941) as well as Night Key (1937) with Boris Karloff.
A whodunnit musical in which the exotic Movita tries to find the real culprit when her brother is unjustly accused of a crime.