Ondina is tasked with teaching the younger mermaids. A mermaid from China joins the pod. During a full moon ceremony, a terrifying beast emerges.

When marine park workers are sent to investigate the reported sea monster, the mermaids must create a credible explanation to stop further inquiries.

Weilan casts a knowledge transference spell on Zac to help him pass a biology test. But more than just science facts transfer from her body to his!

Weilan comes up with the idea of using a Chinese puzzle box to trap the sea dragon. Cam panics when Carly suggests they take dance lessons.

Evie's moon ring lesson with Ondina takes an unexpected turn. At the marine park, Mimmi discovers the reason for a rescued dolphin's distress.

Zac begs Weilan to teach him an Eastern spell few have mastered, which he hopes to use against the dragon. Joe encounters a water ball.

On the eve of the full moon, Ondina and Mimmi defy Veridia's orders. Evie becomes suspicious when she spots Zac and Weilan meeting in secret again.

After overhearing Ondina blaming her for Evie's loss, Weilan runs off. Meanwhile, Mimmi and Ondina combine their powers to try to restore Evie.

Zac realizes a shell he found has magical powers, and he accidentally sends the mermaids back in time five years, where they meet his younger self.

While Ondina teaches the little mermaids to walk on land, her fastest-learning student wanders off and soon runs into Chris and Karl on the beach.

When Mimmi and Chris go on a date at the beach, Ondina goes to great lengths to protect her. Cam tries to lure more upscale customers to the cafe.

Mimmi and Zac are startled by a mysterious yet strangely familiar vision. Cam's dual role as Carly's boss and boyfriend becomes difficult to manage.

Weilan mistakenly makes tea for Rita using a magic growth accelerator. Can the mermaids cure Rita before Mrs. Trumble takes over her principal job?

A priceless artifact recovered by a deep-sea treasure hunter provides a clue as to how the mermaids can defeat the water dragon.

The vision reappears to Mimi and Zac, this time speaking to them. Weilan learns a new detail about the dragon legend that suggests Nerissa is alive.