After losing her position with the Sanctuary, Helen Magnus fights to save Big Bertha not only from the Sanctuary's enemies but from her own allies. In India, Will and Kate hope to restore communication with Kali and stop a catastrophic tidal wave.
Will suffers from the affects of his near-death ordeal, which continue to plague his dreams as he fights to regain his memory. Meanwhile, Helen and Kate try to get to the bottom of the earthquakes that countered Bertha's tidal wave, and Helen faces the judgment of the Sanctuary council.
After discovering that an abnormal egg stored in a safe deposit box has hatched, Magnus, Kate, and Will initiate a hostage situation in order to lock down the smalltown bank – hoping to find the creature they believe has taken a host.
The Sanctuary team responds to a distress call from Nikola Tesla, and finds him trapped in the underground lair of a swarm of multipedes. Meanwhile, Bigfoot looks for justice after a friend from his past is killed.
When a Sanctuary transport is ambushed Walter's super suit ends up attached to Kate, who gains superpowers – and a total lack of inhibition – as she is pursued by a wealthy tech developer.
A werewolf sighting brings Will and Henry to a psychiatric facility in England, which hides an unsettling secret. At the Sanctuary, Magnus and Tesla attempt to decipher the secrets of the holographic city.
Helen brings her old "friend" Adam Worth back to the Sanctuary to try and heal him, revealing to Will his place in the history of the Five. Meanwhile, Helen goes in search of Druitt, and Will makes a disturbing discovery about his mentor.
With new intel from Adam, Helen and John strike out in search of the key to the hidden city. Will receives a visit from an F.B.I. acquaintance looking for help on a case, pointing to a serial killer using Abnormal beetles as his weapon of choice.
Magnus and her team attempt to penetrate Hollow Earth in search of her father and a cure for her illness, and find an advanced civilization that is less than welcoming of outsiders. Back at the Sanctuary, Tesla and Druitt work with Adam to find an alternate way into the city.
After facing the harsh justice of Hollow Earth Magnus attempts to forge an alliance with Ranna, leader of the city of Praxis, which is being rocked by a series of earthquakes. Meanwhile Adam Worth also finds a way to infiltrate the city.
Will's first date with Abby is interrupted by a criminal gang who demand that Will save the life of one of their members, who has been impaled by quills from an Abnormal.
Will and Henry's double date is sidetracked after Magnus asks them to pick up and deliver an Abnormal, which breaks free from containment and flies loose in the city.
While searching a former Praxian stronghold Helen and Tesla stumble into a trap set by the ancient Vampiris race -- along with a lost queen of the species long believed to be extinct. Back at the Sanctuary, Kate learns that a former acquaintance is dealing in Abnormals.
In June of 1944 Helen Magnus, James Watson, and Nigel Griffin join up with the French Resistence on the eve of D-Day, on a mission to ensure the success of the Allied invasion.
A series of unexplained disappearances in Carentan, in the Normandy region of France, brings Magnus and her team to investigate – where they discover a village that is out of time.
Will and Helen find themselves living ordinary lives as unfriendly neighbors in a suburban neighborhood ... until they begin experiencing bizarre visions that suggest their real lives are not what they seem.
The team scrambles after dozens of Abnormals emerge from Hollow Earth and onto the surface, indicating a crisis brewing below ground. John returns with news of Adam Worth, whose experiments in time manipulation now threaten the whole world.
