Plot

While swimming, Zac sees Aquata who flees to the Moon Pool, reuniting with her sister. Aquata informs Sirena that she may return to the pod. Zac uses the trident to find the Moon Pool. With Sirena gone, Lyla and Nixie confront Zac and Cam.

While swimming in the ocean, Zac sees Aquata. She immediately flees to the Moon Pool and is reunited with her sister Sirena. The girls get her up to speed with Zac, the trident, and their ability to walk on land. Zac and Cam discuss the appearance of this new mermaid and interpret it as a sign of reinforcements coming to help the girls take the trident. Aquata informs Sirena that the council has decided that she may return to the pod but Lyla and Nixie still may not. Zac uses the trident to find the Moon Pool. Rita, Lyla, and Nixie convince Sirena to return with Aquata to the pod even though she does not wish to. Lyla and Nixie confront Zac and Cam.—grrlpunk

After encountering Zac in the ocean, Aquata arrives at Mako Island to inform her sister, Sirena, that she has convinced the mermaid council to reverse her banishment. However, the decision does not apply to Nixie or Lyla who nevertheless encourage Sirena return to the pod with Aquata while they continue to try and secure the trident. Meanwhile, Zac discovers the entrance to the Moon Pool on Mako Island and demands answers from Nixie and Lyla. When they refuse to cooperate, Zac declares the Moon Pool off limits for the mermaids. Zac's increasing threats push Nixie and Lyla to confront him at his garage. Zac is too powerful for Nixie and Lyla alone, but Sirena's timely return allows Lyla to grab the trident and whisk it to safety. Sirena vows she won't leave Nixie and Lyla again.