Every night, when the sun says buenas noches, a mother sings a special lullaby to her baby boy: Dónde está mi corazón? Aquí, aquí, aquí en mis brazos.

As he gets older, the boy asks for his song over and over until it's forever in his heart. When the boy grows up and moves away, he teaches the song to his daughters. And now that Abuelita is coming for a visit, the girls plan a surprise for her: they are going to sing her song, "La canción del corazón."