Will takes command of the Sanctuary while Magnus and Druitt search for a critical artifact in London. Knowing that Magnus's only hope for a cure lies in the secret subterranean city, Will ignores her warnings and releases Adam-Hyde in the hope that he will lead them to an access point for Hollow Earth.

Looking to share a quiet, "normal" evening out with Abby, Will and his date are abducted en route to the restaurant by a desperate gang leader who faces certain death without their help. Then, upon learning the abductor's identity, Magnus suddenly ceases all attempts at rescue.

Will and Henry's double date goes awry when Magnus tasks them with an Abnormal delivery.

Helen and Will find themselves in an alternate reality, living as suburban neighbors, who experience unsettling dreams that disrupt their new careers.

As Hollow Earth Abnormals continue to arrive at the surface in droves, Will, Henry, Kate and Bigfoot scramble to prevent all-out war with the Lotus Security Forces. All the while, they are worrying about the whereabouts and safety of Magnus who was last seen heading to Praxis just before the city was destroyed.

Magnus flies to a remote island in Africa to meet with the Sanctuary's new top secret advisor, but lands herself in the middle of a deadly hostage situation.

A mysterious abnormal attacks Abby, and Magnus and Will discover there's only one way to communicate with this unusual enemy - through music.

Magnus is approached by a notorious leader in Hollow Earth who is looking for assistance in building a new home on the surface for his insurgents, but problems arise when the world's government gets involved. Addison reactivates Will's federal commission.

With the new Abnormal Homeland now openly under threat, Henry and Tesla learn that the SCIU weaponized Tesla's work to use against Abnormals. Bigfoot and Kate investigate Caleb's rise to power while Will and Abby look into Magnus' past.