Ariel accidentally frees a dark figure known as the Evil Manta, who tries to take over Atlantica using deception and lies to turn its merfolk people against each other.
Ariel puts on a human bracelet but finds it hard to take it off afterwards. Afraid of how her father would react, Ariel runs away to find the key to the lock of the bracelet.
Apollo, a great Atlantican hero, comes to visit, and Ariel wants to go on an adventure with him, only to learn that he isn't all he's cracked up to be.
Before a family trip to the Carnival of Tides on the tide, Ariel and Arista get into a fight and are 'beached' and Sebastian had to stay and look after them.