Siren

Premise

The coastal town of Bristol Cove, Washington, known for its legends of once being home to mermaids and mermen for centuries, is turned upside down when a mysterious young woman (Eline Powell) appears and begins wreaking havoc upon the small fishing town to look for her captured older sister (Sibongile Mlambo) who was abducted at the hands of the local military. Marine biologists Ben (Alex Roe) and Maddie (Fola Evans-Akingbola) work together to find out who and what drove this primal hunter of the deep sea to land.

By Season Two, more merpeople started appearing in Bristol Cove due to the pollution in the nearby waters and the sonic waves from the oil rig. Additionally, Pownall's paralysis is gradually being counteracted by Ryn's mermaid stem cells.

In Season Three, Ben, Maddie and Ryn contend with the mermaid Tia (Tiffany Lonsdale) who plans to coerce all merpeople tribes/colonies to join her in her fight to overthrow humanity. And Ryn's daughter, who has been carried by a surrogate, must be protected at all costs. To further escalate matters, Ted Pownall has finally acknowledged the existence of merpeople and seems to be on a dangerous path, just as his great-great-great-grandfather had.

Cast and characters

Main

• Alex Roe as Ben Pownall, a marine biologist who helps Ryn when she first comes to shore. He is entranced by her melodious, irresistibly hypnotic siren song, which she deploys on him as a defense mechanism without knowing the full extent of its effects on humans. Ben later becomes Ryn's lover, and his struggle to untangle his affection for her from the obsessive thoughts that result from hearing her siren song becomes a significant part of his character arc. To help Ryn and her kind, he resorts to injecting himself with the stem cells of a partially transformed mermaid corpse and subsequently develops abilities found in merpeople – heightened hearing and reflexes, accelerated healing, and the ability to hold his breath for extended periods of time. At the end of season 3, following the fight against Tia, Ben goes missing in the ocean.

• Eline Powell as Ryn Fisher, a strange young adult mermaid with a dark secret. She comes ashore in search of her elder sister, who has been accidentally captured by fishermen of the North Star fishing vessel. She eventually comes to realize that not all humans are murderous, and becomes Ben and Maddie's lover. To help Ben's mother Elaine, she willingly donates her aquatic stem cells to help counteract the paralysis in Elaine's legs. Upon mating with a bearded merman of another colony when she couldn't find Levi, she has a daughter named Hope.

• Fola Evans-Akingbola as Maddie Bishop, a marine biologist and Ben's girlfriend in season one and two. She works at Bristol Cove Marine Research Center with Ben. Her father is the sheriff of Bristol Cove. Her estranged mother is Susan, who returns after nine months in Season 2. Like Ben, Maddie is entranced by Ryn's melodious, irresistibly hypnotic siren song but doesn't seem to develop the same feelings of possessiveness as a result. She later becomes Ryn's lover.

• Ian Verdun as Xander McClure, a deep-sea fisherman who seeks to discover the truth about the existence of mermaids and mermen. He eventually joins the Bristol Cove Sheriff Department in an attempt to save those he cares about more against the enemy merpeople. In season 3, following the death of Dale, Xander is sworn in as the new Sheriff of Bristol Cove.

• Sibongile Mlambo as Donna (season 1; special guest star season 3), a mystical and deceptively powerful mermaid who is Ryn's older sister. She was unintentionally caught in a fishing net and taken by the military. She was killed, unintentionally, by Xander. Her spirit eventually contacts Helen from the merpeople's version of the spirit world when her body has been grave-robbed. Her ghost later instructs Cami and those on Ryn's side to help Ryn fight Tia.

• Rena Owen as Helen Hawkins, an eccentric woman who seems to know much more about the merfolk than she claims. It is revealed that she is descended from merfolk and shares ancestry with Ben and the other Pownalls. She eventually learns that she has a long-lost relative from the Marzdan family, most of whom are known as hybrids. She discovers that her mother Daphne was one of the merpeople/human hybrids who was promised to fellow hybrid Johnathon Rooney, but had chosen Helen's human father instead. This resulted in the death of Mr. Hawkins, a few weeks before Helen was born. She is eventually contacted by the spirit of her merman love Sarge and, later, Donna's. It is later revealed that she is, in fact, the great-granddaughter of the half mermaid/human daughter of Charles Pownall and his mermaid lover, from her mother's side.

• Tiffany Lonsdale as Tia (season 3), a new mermaid from another colony/tribe of the northern seas around Bristol Cove, Washington. The human locals refer to her as a "sea monster". Her intent on arriving on land is to coerce all other merpeople tribes and colonies to join her in putting an end to humans or perish by her wrath. She choose her name from Tiamat, Water Deity of the Seas. In the past, Tia was caught by humans while she was pregnant and she lost her unborn child as a result of how she was treated. As of "Survivor" and "Life and Death," she has since gained leadership of her own colony and is now bent on unifying all fellow merpeople colonies/tribes to eradicate humanity. To symbolize her higher status as the alpha female, she has orange markings on her tail and chest. She learns of Ryn's infant daughter Hope from Hunter, who she threatens with death if she does not join her and her colony. According to Helen, she is a tyrant. During the final battle, Tia is killed by Ryn causing the rest of Tia's followers to stop fighting and acknowledge Ryn as their new leader.

Recurring

Chad Rook as Chris Mueller, a fisherman who was taken to the military base after being injured by Donna. He was held at the facility where he escaped with Donna, only to later fall under their power-mad influence in harvesting the merpeople and their superhuman abilities for their own purposes.

Curtis Lum as Calvin Lee, an Asian fisherman who is also a friend and roommate of Xander. His girlfriend is Janine, who works at the Anchor cafe. In Season Three, he proposes to her and she accepts. They get married in "Til Death Do Us Part".

Ron Yuan as Aldon Decker, an expert on merpeople who worked for the military for many years. He experimented on and became obsessed with Donna and her siren song which prompted him to drown himself once Donna herself had died.

Gil Birmingham as Dale Bishop, the sheriff of the Bristol Cove Sheriff Department and Maddie's stepfather. He is descended from the ancient Haida people. He is the third human to discover the existence of merpeople and becomes another ally. Since the Season 3 premiere "Borders," he has been looking for Nicole at the behest of Xander. During the sound-based terror attack on Bristol Cove and its neighboring towns, Dale is among those affected. Before succumbing to it, Dale helped a crashed car where a mother driving it was affected. This left Maddie devastated and he is succeeded by Xander.

David A. Kaye as Jerry, a man who works at Bristol Cove Marine Research Center along with Ben and Maddie. He is the one who makes fake IDs for the merpeople (thereby officially naming them) in "Oil and Water"; completely unaware of their true selves and nature.

Garcelle Beauvais as Susan Bishop (voiced season 1, season 2), Maddie's mother and Dale's ex-wife who tries to make amends with her estranged family.

David Cubitt as Ted Pownall, Ben's father, head of the town's fishery industry and whose great-great-great-grandfather Charles first discovered merpeople in the mid-1800s. He eventually comes to realization that his family was anything but crazy since "Revelations" when he saw Tia trying to kill him but was saved by Ryn. Now distrustful of mermaids and the probable threat they represent, he seems to have set on a dangerous path as his great-great-great-grandfather Charles had.

Sarah-Jane Redmond as Elaine Pownall, Ben's mother who became paralyzed after a boating accident a decade earlier. She is eventually given renewed treatment from none other than aquatic stem cells from Ryn's mermaid DNA. As a byproduct, she is capable of holding her breathe underwater for about four minutes, though her legs remain somewhat paralyzed.

Tammy Gillis as Marissa Staub, the deputy of the Bristol Cove Sheriff's Department.

Hannah Levien as Janine, Calvin's girlfriend who is a bartender at the Anchor. She eventually accepts his proposal, and they get married in "Til Death Do Us Part."