Roberto Moran (Mariano Mores) has just arrived in Buenos Aires from the provinces to work in a foundry. He can play the bandoneón by ear but wants to have proper training in music at a conservatory run by a frustrated old musician, Don Matias (Ricardo Galache). The old man first rejects both Roberto and his instrument, but after hearing him play, he changes his mind and takes him on, though forbidding him to play popular music, which he despises.
A female Argentine tango singer in occupied France (Libertad Lamarque) gets romantically involved with a Resistance member (Juan José Miguez). A local Gestapo commander (Alberto Bello) tries to convince her to infiltrate the Resistance in exchange for her little daughter's safety.