The Dark Hand releases Bai Tza, the Water Demon. She seeks out her old kingdom – Atlantis, but when she finds it in ruins, she chooses to drown San Francisco as a new home with some information from Finn. Meanwhile, Valmont manages to render Shendu out cold and seeks help from the Chans to exorcise him from his body. However as Uncle is preoccupied with finding a spell to stop the flood, so the Chans with Valmont have to face Bai Tza without him.