When a US citizen is murdered at the Mariachi Plaza, the Criminal Investigation Unit starts investigating the case by order of the chancellor, since the victim is the nephew of the United States Ambassador. According to the autopsy, the crime was committed using darts with venom extracted from different Mexican snakes. The suspect appears to be dressed in pants similar to those worn by mariachis. There are two suspects: the son of a tailor, fitting the murderer's profile due to his aversion to foreigners and the fact that the tailor shop made mariachi suits, and a trumpet-playing mariachi who displayed xenophobic behavior. Unfortunately, Detective Barraza is struck by a poisoned dart
