Life is great for Sissy Dominguez. She has the best mom and dad and the world's BESTEST best friend: Rosario. But one day everything changes, when mamá y papá return from a trip with a surprise for her! The surprise was not at all what Sissy expected. Her parents seem to have changed forever and her grandma blames the mysterious el Chiquitín.With no clues to go on, it is up to Sissy and her best friend Rosario to figure out what's in the mysterious package that is drastically changing her family's life. Can you help Sissy and her best friend find clues to solve the mystery of el Chiquitín and save their parents?