Maddie and Ben rescue Xander and Calvin from the North Star.
The mermaids say goodbye to Sarge and his body is buried by sand.
Ben's dad confronts him about the attack on the oil rig.
There is a two week time jump.
Helen and Rick decide to tell Rick's sister the truth about thier family.
Maddie tells Ben she misses Ryn and he tells her that he's been listening to the tape of her Siren song. They listen to it together.
Nicole comes to see Xander and he tells her to leave. She's goes to Ben and Maddie to ask if they know where Ryn is.
Ryn comes back and tells Helen about Sarge's death before reuniting with Ben and Maddie. She tells them about her deal with the militsry and they want her to go back to the water. Ryn refuses to leave them.
Ben, Maddie, and Ryn go to the ER where Ben's mom has just been admitted.
Xander gets a job at the bar.
Richard's sister doesn't believe they're related to mermaids so Helen plays off his story as nerves.
Ben and Maddie realize their may have been video footage of the night the oil rig was attacked. Nicole comes to the ER to try and tell Ben about stem cell research from the mermaids that could help his mom.
Ryn is able to take away Ben's mother's pain.
Ben's dad sees a video of one of the mermaids in the water at an impossible depth.
The mermaids find another mermaid underwater.
Ben goes to talk to Nicole about the research.
Xander comes to the hospital and tells Maddie he isn't sure if he wants to file the insurance and get back on the water.
Maddie agrees to help Ben find a cure for his mom by doing research with the military.
Richard's sister takes Richard and Helen captive.
Ben, Maddie, and Ryn go to the lab and Ryn starts testing.