Through different situations, the narration is introduced into the life of old García (a lonely and enigmatic man who lives and works in an astronomical observation center that has been operating since the sixties in the city of Santa Fe), of Marcelo ( a young man passionate about the unfathomable mysteries of the cosmos) and Noelia (a student who will start working as Garcia's assistant).

The discovery of a mysterious letter turns the archaeological remains of Santa Fe La Vieja into a playground for adventure. The mission Mina's grandfather entrusts his granddaughter with will unravel a web of intrigue that will reveal stories of a city from bygone times. A city built on the shores of a freshwater sea that still has secrets to tell.