A month has passed since Ryn and her sister went off into the ocean and disappeared. Ben and Maddie are trying to get back to being a normal couple when they see that Ryn's tracker is working again.
Turns out Ryn and her sister are back and need food because there is none in the ocean. They are hungry and Ryn trusts them while her sister just wants to go back into the water. This leads to a confrontation between both sisters, with Ryn staying with Maddie and Ben while her sister Donna disappears.
Helen agrees that they should return to the water and she ends up finding Donna, then takes her to her house and reveals that she is on her side because she is one of them.
Ben starts to show interest in his dad's business because he thinks they are hunting everything from the oceans and needs proof. He gets access to his dad's laptop and finds out he was right.
Maddie has lunch with Elaine where Ben's mother alludes to the fact that she is just a rescue to Ben. FInally Maddie makes it clear that she is more than that.
Maddie and Ryn share a kiss when they talk about how they missed each other.
Meanwhile, the people from the lab are still in search of Donna and are trying to figure out how to capture the mermaids and prevent them from escaping again.