The Mermaid Discovery 

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

The Lure

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

Interview with a Mermaid

Dale and the local police's investigation points directly to Ryn; Xander and Calvin's search for Chris heats up.

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On The Road

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

Curse of the Starving class

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

Showdown

When Ben and Maddie attend his mother's fundraising gala, where an unexpected guest shows up and offers to put an end to the overfishing.

Dead in the Water 

Ryn is taken in for questioning; Ben and Xander return to the deep sea to search for answers, only to be met by an uninvited guest.

Being Human 

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

Street Fight

Donna and two members of her colony come ashore, and begin wreaking havoc throughout the town.

Aftermath 

The enchanting siren song takes hold of Ben and Decker; Dale must answer for the escalating crime in Bristol Cove.

The Arrival

A new threat wreaks havoc as more mermaids land on the shores; Ben tries to cope with the siren song's aftereffects.

The Wolf at the Door

Ben, Maddie, and Ryn try to keep the new mermaid pack hidden from the town's Mermaid Beauty Contest.

Natural Order

Ryn fights to maintain leadership of the pack; Helen discovers more about her family lineage.

Oil & Water

Ryn looks for new housing for the mermaids; Ben becomes Levi's mentor; Maddie continues to struggle with her mother's presence.

Primal Instincts

Maddie finds herself in a dangerous situation; Ben and Xander reconcile to get the mermaids back into the water.

Distress Call

Dale copes with the fallout from Maddie and Ryn's encounter with the man from Susan's past; Katrina tries to get the rest of the pack to join her side.

Entrapment 

Tensions rises following a shocking discovery; The water tank starts to have an adverse effect on the mermaids; Ryn makes a deal with a complicated ally.

Leverage

Mermaids and humans join forces to stop the oil company, but their efforts have a devastating effect.

No North Star

Everyone deals with the fallout from the oil rig attack; Ryn returns to land to follow through on an agreement she made with the military.

All In

Elaine's treatment from the military's medical trial comes with side effects to the mermaid cells; Helen and Rick learn more about the hybrid status. 

Mixed Signals

Maddie and Ben contend with how to help Ryn; When Maddie gets sirened, the group strive to uncover how the siren song really works.

Serenity

Ben, Maddie and Ryn venture under the sea to a special place in Ryn's homeland that could help with their conditions.

The Outpost

Ryn must return to her colony for mermaid mating season; Ben and Helen hunt down the hybrids when they lure a mermaid to a remote location.

The Last Mermaid

An unsuccessful mating season leads to questioning the possibility of the mermaids procreating on land; Ryn brings a new mate for the good of the colony.

Sacrifice

Ben and Xander deal with a shocking discovery about Chris and his connection to the military; Helen and Maddie reluctantly seek help from the hybrids as the threat of extinction looms.

A new world order

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

Borders

As an old friend visits Helen, a new mermaid arrives leaving Ryn questioning their motives; Maddie learns the truth behind Ian's death; Ben fights for his mother's treatments; Xander is inspired to take on more responsibility.

Revelations

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; Ted revisits the past.

Survivor

Ryn learns the secret existence of her unborn child; Ben sets out on a dangerous path to help his mom; Xander tries to establish himself in his new career; Helen consults with Eliza to help contact Sarge.

Life and Death

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.

Mommy and Me

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

The Island

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 explores his family lineage.

Northern Exposure

Ryn, Ben, and 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.

'Til Death Do Us Part 

Ryn, Ben, and Maddie must protect Bristol Cove from Tia's army; Ben's injections produce unexpected results; Xander juggles best man duties at Calvin's wedding while also helping Helen.

A Voice in the Dark 

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 reconnect with Ryn.

The Toll of the Sea 

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; Helen and the hybrids help restore order.