Elijah undertakes Klaus' royal responsibilities and attempts to restore peace in the kingdom as the latter tries to distract himself. Hayley finds that Sabine was honest while a desperate and confused Marcel prepares to plot against the new powers that be.moreless
Davina loses control her powers and becomes violently ill and sends shockwaves, winds and rainstorms through the French Quarter. Elijah approaches the Sophie for answers and is informed that the Harvest Festival needs to be completed to save Davina. Hayle angers Elijah when she comes clean to about her role in Sophie's plan to complete the Harvest by consecrating Celeste dubois’s remains. Meanwhile Marcel takes Davina into hiding to prevent the Harvest ritual from being completed.
Marcel is surprised when Klaus reveals him things about his past. Cami tries to understand what some messages she found mean and she finds out information about Klaus' past. The human factions decide to take action which lead to violence. Hayley learns of a plan to harm the werewolves in the bayou, so she asks for Elijah's and Rebekah's assistance. They run into Eve, another werewolf, who shares shocking information.moreless
Rebekah has a difficult decision to make and she addresses Father Kieran for help. Elijah and Klaus quarrel and Elijah needs to face the consequences of that. Hayley supports him, but she is distracted by someone who can can give her information about her past. Cami tries to depict a message. Marcel finds information about Klaus that upset him.moreless
Mary enjoys her romantic time with Francis, until he ends up reunites with Olivia his ex, who was attacked in the woods. Mary is unthreatened by her arrival, until she reveals her upcoming attempts to be with Francis, even as his mistress, to Mary's face.moreless
Tomas turns out to be not quite the gentleman he wanted Mary to believe. Francis, Sebastian and Mary try to uncover the truth about an English ambassador, who's life, and the peace between whole countries lies in the balance, all while attending a masquerade ball.moreless
The Scottish borders are being threatened with war, and King Henry won't agree to send adequate help for Mary. Sebastian and Francis are at odds, and the future Prince of Portugal begins to find interest in the still unmarried Queen of Scotland.moreless
Mary and the English kingdom know about the fragility of her arranged marriage, so Mary seeks Francis' help to protect their alliance, and engagement. Meanwhile Queen Catherine finds out a loose end hasn't been taken care, and someone might be able to link her to her crime.moreless
Pete, Myka, and Steve team up with a U.S. Marshal to track down two prisoners who escaped prison during a volcanic eruption.
The team races to stop Stanton's plan to activate the mini-stims across the continent. Meanwhile, a wounded Rosen seeks revenge for his daughter by going after the Alpha personally.
While Rosen interrogates an Alpha prisoner, Gary and Bill try to rescue Skylar from Parish.
Kat returns to the team as they set out to find Stanton's secret weapon... and protect him. Meanwhile, Senator Burton challenges Rosen's methods of fighting rogue Alphas.
Difficult times arise for Rosen and his team as the loss of a loved one shocks everybody. Meanwhile, a woman abandons a baby boy at the office and Gary takes him under his wing.moreless
Stanton Parish plans works to engineer a city-wide blackout... and Hicks defects to help him.
While Kat takes on her first mission tracking down a street drug that gives normal humans temporary Alpha powers, Rosen discovers the identity of the mole.
Rosen and Parish face off against each other after a young Alphas emerges with the deadly ability to control minds.
Rosen goes to Alpha gadgeteer Skylar Adams for help dealing with Stanton Parish, but Skylar and her daughter are soon at risk when Stanton gets too close.
An Alpha goes insane and his delusions lead him to abduct Rachel. However, when the rest of the team search for her, they find themselves entangled in a series of bizarre situations.
The team discover that the Alpha they're hunting is their missing teammate, Nina, whose powers are going out of control.
Cameron and Bill go undercover as fighters as an underground arena and meet a young girl with a unique power. Meanwhile, Gary considers moving out, Rachel bonds with the team's new tac leader, and Rosen tries to find out more about Stanton Parish.moreless
Rosen and his team look for an Alpha with a vendetta, but the hunter becomes the prey when the Alpha comes after them.
Eight months after Dr. Rosen's startling announcement to the world about the existence of Alphas, the government has had him committed. His Alphas, which have gone their own ways, must decide whether to reunite and save their friend when Rosen is called in to deal with an Alpha prison break.moreless
In the series finale, the Department of Defense's closure of Eureka is delayed by random wormhole materializations.
The doubles steadily take over GD, which means Fargo, Allison and Zane are in a fight for their lives and everyone else's as they try to avoid capture and fix the problem.
The Department of Justice arrives to investigate Grace, and Henry struggles with his conscience. Holly receives a message that triggers a chain of events. The question is whether it's her actions or Fargo's malfunctioning signature achievement that are causing the scary incidents all over GD and the town.moreless
Carter and Allison's perfect honeymoon is interrupted when sabotage is discovered in Eureka. Elsewhere, Holly faces another hurdle to remain intact.
While under the influence of a smart drug, Carter becomes a genius like everyone else in town and starts to change the laws of physics. Unfortunately, his condition soon endangers all of Eureka, including Allison's brother who is in town just to meet his new brother-in-law.moreless
Carter and Allison's romantic plans run afoul of a rogue submarine, and it's up to Jo to save their lives … if she can fix the mess at Global Dynamics caused by an out-of-control prankster in time.moreless
When the ship with the Astraeus crew returns to earth, its occupants discover that four years have elapsed and time isn't the only thing that has changed.