On the fifth anniversary of Klaus' defeat, Marcel is king of the city and welcomes the un-sired vampires to New Orleans, only to find they pose an unexpected threat to his rule, leading him to seek counsel from an unlikely source. Meanwhile, as Hayley closes in on the cure that will allow her to revive Elijah and the slumbering Mikaelsons, she faces a final task that will force her to make a ruthless decision.
After being cured and woken, the Mikaelson siblings join Hayley in an effort to rescue Klaus from captivity - even if they must face Marcel in the process. Meanwhile, Klaus' demons materialize in unexpected ways as he suffers from the effects of the Tunde Blade, and Vincent investigates a haunting that will prove to be much more sinister than he could have imagined.
After five long years apart, Klaus attempts to reconnect with his daughter, Hope. Even as father and daughter bond, the rest of the family is still in turmoil. Elijah mediates a conflict between Hayley and Freya to determine the best way to protect the family. Meanwhile, in New Orleans, Vincent tells Marcel terrible secrets about his ex -wife, Eva Sinclair, even as they begin their search for a mysterious witch who plans to sacrifice a group of innocent children - including Hope Mikaelson.
Desperate to save her daughter, Hayley turns to Marcel for help uncovering information about the mysterious force that has set its sights on the children of New Orleans. While Klaus remains behind with Hope, Elijah and a reluctant Vincent join the hunt, which puts them on a dangerous collision course with an unlikely new threat. Finally, Freya and Keelin must put aside their differences as they embark on a journey that may alter the power dynamic in New Orleans forever.
After being marked by The Hollow's dark magic, both Klaus and Marcel experience the symptoms of a malevolent haunting, forcing the two adversaries on a unhappy collision course. Meanwhile, Hayley and Elijah head out to speak with Mary after Hayley uncovers a mysterious link between the dark magic and her former wolf pack. Finally, as an exhausted Freya risks her own life to cure Klaus' infection, a guilt-ridden Keelin must decide whether to honor her hypocratic oath and help Freya - or flee the Mikaelson's forever.
When it's discovered that The Hollow has employed a mysterious servant to do its bidding, Klaus and Elijah host an elaborate party in order to lure the new threat out and uncover its identity. Feeling a sense of responsibility for The Hollow's resurgence, Vincent uses his magic to help the Mikaelsons root out this latest threat. Meanwhile, after uncovering information about who may have been behind her parents' death, Hayley turns to Freya to help unlock her memories from that fateful day.
When it's discovered that The Hollow's latest servant is on the loose, Freya places a protection spell on the compound, forcing Klaus, Hayley and Hope to remain inside. Meanwhile, Elijah takes matters into his own hands when Vincent is reluctant to perform a dangerous ritual needed to strengthen their defense against The Hollow. Finally, while Freya enacts a risky plan that brings her face to face with their latest threat, an unexpected twist leaves her life hanging in the balance.
After being summoned by the ancestors, Hayley and Klaus travel to the ancestral world and come face to face with Davina, Klaus' former foe and the one person who holds the secrets to The Hollow's demise. Meanwhile, old wounds are re-opened when Elijah and Marcel are forced into an uneasy alliance. Together, they meet with Alaric who has tracked down a crucial artifact that could help in their fight against The Hollow.
When The Hollow sends a terrifying message to Vincent, he must team with Haley and Freya to embark on a desperate mission to stop the Hollow once and for all - even if it requires a heartbreaking sacrifice. Refusing to allow anyone in his family to pay the high price of defeating their enemy, Klaus makes a surprising alliance and enacts a plan that threatens to change the Mikaelson family forever.
Klaus requests that his estranged siblings Rebekah and Kol return home to stand by their family against The Hollow. Meanwhile, Freya recruits Hayley for a dangerous journey that will put both their lives at risk - but may be the sole means of saving someone they love. Elsewhere, tensions rise when Marcel leads a hunt for The Hollow - putting him on a collision course with the person he was least prepared to face. Finally, as Kol continues to mourn the loss of Davina, he is forced to consider the lengths he'd go to see her again.
When its discovered that The Hollow is using a magical totem to fuel her power, Freya enlists Rebekah and Klaus' help to locate and destroy it. Elsewhere, an ultimatum by The Hollow puts Kol at odds with his own siblings, while an unexpected run-in forces Marcel and Rebekah to confront the growing tension between them. Finally, The Hollow's plan for Hayley leaves her in the fight of her life.
When The Hollow targets the most vulnerable Mikaelson, Klaus is forced to rely on Vincent, who believes he can use The Hollow's own dark magic to defeat their enemy for good. Meanwhile, as Marcel worries that Vincent's plan might backfire, the King of New Orleans decides on a deadly backup plan of his own. Elsewhere, after falling victim to The Hollow's manipulations, Hayley struggles to figure out Hope's future in New Orleans, while Freya must confront her darkest fear.
The Mikaelsons find themselves out of options as they face the all-powerful and un-killable entity known as The Hollow. With the life of Hope at stake, Vincent proposes a final, desperate plan - one that will force Klaus, Elijah, Hayley, Rebekah and Freya to make the greatest sacrifice their family has ever endured.