The coastal town of Bristol Cove, once known for being home to mermaids, is turned upside down with the arrival of a mysterious girl.

Ben and crew of The North Star uncover a device emitting a strange sound. Meanwhile, Ryn finds shelter in the home of the local folklore expert.

Dale and the local police’s investigation starts pointing directly to Ryn, meanwhile Xander and Calvin’s search for Chris heats up when they locate the nurse who works at the military bunker.

When the military facility goes on high alert, Chris manages to escape, but he’s not the only one who gets out.

Ben begins to investigate some suspicious overfishing, meanwhile Decker ramps up his efforts to find his escaped mermaid and shows the true extent of his influence.

When Ben and Maddie attend his mother’s fundraising gala, an unexpected guest shows up and offers to put an end to the overfishing that’s threatening the lives of the mermaids in Bristol Cove.

When Ryn is taken in for questioning, Maddie rushes to her rescue. Meanwhile, Ben and Xander return to the deep sea to search for answers, only to be met by an uninvited guest.

Bristol Cove mourns a loss causing Ryn to experience a new human emotion.

Donna comes ashore with two other members of her colony to bring Ryn back home. When mermaids once again begin wreaking havoc throughout the town, Dale tries to put an end to it once and for all.

In the season finale, the enchanting siren song takes hold of Ben and Decker. Meanwhile, Dale must answer for the escalating crime in Bristol Cove.

With more mermaids landing at Bristol Cove’s shores, the threat of discovery increases. After his encounter with the siren song, Ben tries to cope with the after effects. Maddie’s mom returns to town …

Ben, Maddie and Ryn desperately try and keep the newly arrived mermaid pack hidden from the rest of the town, but the new mermaids’ quick degradation on land forces them to get them back to the sea un…

Ryn fights to maintain leadership of the pack when the other mermaids question her loyalties. Ben interferes in a mermaid ritual causing friction between himself and Ryn, meanwhile, Helen discovers mo…

Ryn decides they need to find another solution for housing the mermaids, as hiding them becomes increasingly difficult. Ben becomes a mentor to Levi as he tries to learn how men behave on land, while …

Ryn continues to try to teach the other mermaids to be more human in order to better assimilate, but some are starting to resist her, causing Ryn to wonder if she herself is becoming too human. Maddie…

Dale copes with the fallout from Maddie and Ryn’s encounter with the man from Susan’s past, while Katrina continues to persuade the rest of the mermaid pack to get on her side—even if that means brute…

Tensions are rising following a shocking discovery. And living in a tank rather than the ocean is starting to have an adverse effect on many of the mermaids. Hoping to save her kind, and help her huma…

Mermaids and humans join forces in a radical plan to stop the oil company, but their efforts have a devastating effect. And facing an uncertain future, Ben, Maddie and Ryn come together for a romantic…

Ben, Maddie and the other humans deal with the fallout from the attack on the oil rig, while the mermaids reacclimate to their ocean home. Ryn comes back to land to follow through on an agreement she …

With Elaine Pownall’s health worsening, she seeks treatment from the military’s medical trial using mermaid cells, but the procedure doesn’t come without side effects to the mermaids. Meanwhile, Helen…

Maddie and Ben contend with how to help Ryn knowing that in order to help Elaine get better, they will need to continue the procedures on Ryn. Meanwhile, when one of the group gets sirened, there is m…

Ryn goes back to the ocean to get help for Ben and Maddie’s conditions but discovers that continuing to go back may get harder than she realized the longer she’s on land. But when they learn that ther…

Mermaid mating season has begun, with Ryn knowing she will need to go back to the sea to help her colony. The hybrids convince one of the mermaids to come with them to a remote location, leading Helen…

Mating season turned out to be less successful than everyone had hoped, leading them to question the possibility of the mermaids procreating on land. Ryn brings a new mate ashore for the good of the c…

Ben and Xander are left dealing with a shocking discovery about Chris and his connection to the military. Meanwhile, Helen and Maddie reluctantly seek help from the hybrids as the threat of extinction…

Ben faces a choice that has rippling consequences amongst mermaid, hybrid and human alike, as the truth about mermaids is exposed.

As an old friend visits Helen, a new mermaid arrives leaving Ryn questioning their motives. Maddie learns the truth behind Ian’s death, as Ben fights for his mother’s treatments. While Xander is inspi…

When another mysterious death is uncovered in Bristol Cove, Ryn suspects Tia. Maddie befriends a new acquaintance in Seattle. Helen warns the hybrids of trouble. Xander begins training and Ted revisit…

Ryn seeks help only to learn the secret existence of her unborn child. Ben sets out on a dangerous path to help his mom, while Xander tries to establish himself in his new career. Helen consults with …

Ben and Maddie help Ryn guide her surrogate though a life-threatening delivery. Helen and Xander deliver a hybrid corpse to Beth at The Ranch. Xander faces danger on the high seas during a ride-along …

Ryn returns to land to explore human motherhood. Maddie and Robb come across a gruesome discovery. Ben experiences mysterious side effects and Ted confronts Helen.

Ryn discovers a refuge of injured mermaids that escaped Tia’s violent takeover. Ben and Xander get caught in a battle with Tia’s troops. Maddie feeds Robb half-truths to secure his discretion. Ted exp…

Ryn, Ben, Maddie must recruit new allies in the fight against Tia. Helen seeks answers when she’s haunted by Donna’s spirit. Tia obtains dangerous weapons she plans to use in her fight. Xander struggl…

Ryn, Ben and Maddie must protect Bristol Cove from Tia’s army. Meanwhile, Ben’s injections are producing unexpected results, which alarms both him and the others. Xander juggles best man duties at Cal…

Tia unleashes a deadly attack on Bristol Cove. Ryn, Ben and Maddie race against time to find a cure for Xander’s mysterious illness, while anticipating Tia’s next move. Baby Hope returns to land to re…

In an effort to save Hope, Ryn and Ben confront Tia in an undersea battle between the mermaid tribes. Maddie and Robb work to find a cure for Xander, while Helen and the hybrids help restore order. Te…