LKA target investigator Hanna Landauer and her new partner Lars Röwer are facing a crucial test in their current case: nine years ago, Gisela and Uwe Tetzloff kidnapped an industrialist and extorted ten million for ransom. Although the police managed to catch the couple, the money and their unknown accomplice remained missing.
Now that the two hostage-takers are being released from prison, they finally want the reward for their silence. They skilfully go into hiding under false names and flee to South America. Hanna Landauer and Lars Röwer pick up the trail again in Montevideo.
In order to locate the gangster couple in the metropolis, the two cling to one single clue: Gisela's passion for the tango. Night after night, the two undercover investigators scour the tango bars in Montevideo at the so-called milongas.
Exhausted from the exertion, Landauer confides in her ex-boyfriend Rossmann, who arrested the couple at the time and has since left the service. Röwer, on the other hand, suspects that he won't get any further on this assignment abroad if he sticks to the service regulations.
The situation worsens when it becomes clear that the two target investigators are being followed and are in great danger. Landauer and Röwer have no idea who else is involved in this dangerous game of nerves.