Conclusion. 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 in the Season 4 finale.
Part 1 of 2. Caleb asks Magnus to help broker a peace deal between his insurgents and the governments on the surface; Addison reactivates Will's federal commission; Tesla resurfaces.
Season 4, Episode 11
A quest to capture a legendary Abnormal in Bolivia leaves Will and Magnus injured and trapped in a cave-in, where they confront truths about themselves and their relationship; Henry records video letters to a special someone while working on an invention.
Season 4, Episode 10
Kate Freelander resurfaces with a warning about a Hollow Earth plot against an above-ground target, and evidence suggests that Bigfoot may be involved in the attack.
Season 4, Episode 9
Adam Worth resurfaces as an avatar in a virtual Sanctuary, where he imperils Magnus and Tesla in a bid to enter the real world.
Season 4, Episode 8
An Abnormal's attack on Abby leaves her requiring treatment at the Sanctuary while Henry and her FBI partner Gavin retrace her steps to determine what happened.
Henry, Declan and a team from the UK Sanctuary go to the Bering Sea to investigate a mystery on a shipwrecked icebreaker, where the crew has killed the Abnormals on board and each other.
Two flying Abnormals land on the Sanctuary seeking Magnus' help; Will is temporarily blinded during a riot in Monrovia.
The team tracks an Abnormal fugitive, and discovers that Tesla is the head of a secret research lab for a Homeland Security agency that conducts tests on Abnormals.
Season 4, Episode 4
A hostage situation unfolds when Magnus flies to a remote island off of Africa to meet the Sanctuary's new financial adviser; a shipping container mix up has Will and Henry tracking a missing Abnormal.
Magnus must explain a mission that went awry to a UN official as the Sanctuary faces scrutiny following the barely averted Abnormal uprising; Will's girlfriend turns up with an unforeseen problem.
Season 4, Episode 2
Hollow Earth Abnormals amass at the surface with the Lotus Security Forces poised to take action as Magnus' people try to prevent an all-out war between humans and Abnormals.
Season 4, Episode 1
Magnus goes to 1898 London to try to stop Adam Worth from saving his daughter, which would alter the current time line in the Season 4 premiere.