Ben faces a choice that has rippling consequences amongst mermaid, hybrid and human alike, as the truth about mermaids is exposed.
Ben and Maddie are on a high-speed chase trying to rescue Ryn from Ian. However, Ryn saves herself as the drugs wear off giving her the chance to take the wheel leading the car into the water. The car fills up with water as it sinks leaving a panicking Ian trapped. Ryn uses her supernatural strength to escape while Ben rescues Ian. Despite the gratitude, Ian rats outs Ryn just two days later on the news. This leads to Ben and Maddie along with Ryn to go into hiding for two months as Ryn is the number one target of everyone who wants to exploit her. Canada offers asylum to any merpeople on land and the trio decides to go there.
Meanwhile, dozens of hybrids are detained by the government to be tested on, while full-blooded merpeople are being hunted for the unique properties of their merfolk physiology. The gang almost makes it to Canada, however, they are sold out by none other than Ben's father, which leaves Maddie getting killed in the process.
Flashback to Ben in the water it's revealed he has been foreseeing a bad future if he saves Ian so he leaves him to die lying to Maddie that he was already dead when he resurfaces. Ryn is disappointed that she's not with child as Ian sabotage that chance for her not knowing that her surviving embryo is thriving and growing in a hybrid named Meredith, as her parents Ryan and Leena have planned this all along in order to have a full-blooded merperson granddaughter or grandson of their own.
- Ian Sutton (final appearance)
- Ben Pownall
- Maddie Bishop
- Ted Pownall
- Dale Bishop
- Elaine Pownall
- Calvin Lee (flashfoward)
- Janine (flashforward)
- Xander McClure (flashfoward)
- Cyrus (debut appearance; flashforward)
- Marissa Staub (flashfoward; cameo)
- Teenage Mutant Ninja Turtles has a two-part episode with the same title in its fifth season.
- The difficult choice Ben makes refers to him "choosing to save Ian from a watery grave"
- Having witnessed Ryn transform and abducted her, Ian exposes the existence of merpeople on live television, describing them as "highly evolved apex predators."
- The people of Bristol Cove learn that mermaids and mermen have existed all along. Though this is later proven to be false; nothing more than an apocalyptic future envisioned by a frightened Ben, had he chosen to spare Ian:
- Ted Pownall now sees that his great-great-great-grandfather Charles was never crazy, that he had indeed fallen in love with a mermaid and had a half-human, half-mermaid child with her, and that he himself had actually encountered such a creature ten years ago while trying to save his newly paraplegic wife from drowning.
- Xander is revealed to have kept the lure used to entice other merpeople to the military in said episode. To Ben's dismay, he only cares about how much money is offered for capturing a mermaid.
- Thanks to Ryn's mermaid stem cells, Elaine has made significant progress; capable of lifting herself off her walker although this is only in the alternative timeline.
- In the alternate timeline Beth Marzdan had tried to escape with several other merpeople/human hybrids, but was shot to death in the attempt. As a result, all Hybrids are implanted with tracking devices.
- It is revealed that Bryan is the husband of Leena and that Meredith is their daughter, all of whom had schemed to steal the unborn child of Ryn and her mate to have a full-blooded child of their very own
- Ted: "Ben, you can talk to these guys. It's not too late."
- Ben: "What, I give her up and save myself, is that it? That's what I thought."
- ―Ted tries to convince Ben
- Ryn: "Why did he take me?"
- Maddie: "He wanted to share you with the world. That would have been bad."
- Ryn: "No more. He is dead now."
- Maddie: "You did everything you could."
- ―Ben, Ryn and Maddie discuss their escape from Ian Sutton
- Leena: "It's safe."
- Meredith: "For me to carry one that's not my own?"
- Leena: "There's a lot we don't know. I'm seeing accelerated development beyond that of a human fetus, but that heartbeat is strong. It's a positive sign."
- Bryan: "That's my girl. We soon will have a full-blood of our very own."
- ―Leena and her family about Ryn's baby implanted in Meredith
- SpoilerTV — "Siren - Episode 2.16 - New World Order (Season Finale) - Promo + Press Release" (July 26, 2019)