Antonia Guererro, who her friends call Kachorra, is a young girl from a poor neighborhood who lives with her father Francisco, a bar owner, and with her brother Santiago. She works as an outdoor coffee and sandwich seller. One day she is at the wrong palce at the wrong time when she tries to help nun Catalina with keeping her orphanage which she loves. The police find shocked Kachorra with a dead body of notary Armendaris and she is accused of his murder. Antonia is taken into custody and she is cut off everyone she loves. Her future does not look good. It is most likely that she will not see her family or fiancé Germán ever again.

But in the end it looks like luck is on her side, when she is being transported to the prison, the police car crashes with a taxi where Rosario Achaval is trying to get to her first day at work. Kachorra wakes up first after the accident. She thinks that Rosario is dead and decides to take her identity. She takes her documents and luggage and after calling an ambulance she runs away. In a nearby gas station she cuts and colors her hair into red and dresses into Rosario's clothes. Soon she goes to the house of a rich family where she thanks to her qualifications is hired as a tutor for their children. From this time Kachorra needs to pretend she is the thirty year old Rosario who speaks many languages and studied in USA.