Elena, Fiona, and Marcus travel back in time to Mexico during the reign of the Aztec empire. There have been sightings of a powerful mermaid named Tlanchana, thought to be causing a devastating drought. The monster hunters learn about Aztec festivals, music, and culture on the streets of Tenochtitlan. Follow the team as they race against the clock to return a stolen crown to Tlanchana, known for being more wicked than sweet. Will she end the drought and remain hidden from the human world?