Ashley and Henry are captured by the Cabal after breaking into their weapons factory. While being restrained Ashley learns from Dana Whitcomb that the plan they have for the virus to be released worldwide will still go ahead. In a different part of the facility Henry is being kept strapped to a hospital bed. The Cabal intend to use chemicals to turn him into his abnormal state, and keep him that way.
Magnus and her team have to face the possibility of international biological warfare when a virus infects the abnormals, causing them to attack humans. John Druitt makes an unwelcome return to the Sanctuary as, he too, sees the significance of the situation and he tells them the Cabal are behind it. The leader of the UK sanctuary, Sir James Watson, contacts Helen and confirms John's story about the Cabal, meaning she has to work fast.
Magnus and her team rescue the passengers of a sinking ship off the coast of South Africa. Back at the Sanctuary, one of the passengers is found murdered and Druitt becomes the prime suspect.
When Danny, an old friend of Will, goes missing, his wife contacts him asking for help. With the aid of Helen and Ashley, Will starts searching and they find themselves in an abandoned factory. There is no sign of people, but the team come to the conclusion that something took place there after they find dried blood and the drug epinephrine. They come to the conclusion that the building is being used as a place to train fighters.
Helen reunites with Jimmy who transports an elemental Abnormal to the Sanctuary. However they are tracked down by the underground Mobsters. Kate proves her loyalty and bonds with Jimmy over a common history they share
Magnus and Will try to retrieve a sea creature from the coast of Louisiana, but the Abnormal breaks lose in mid-flight, resulting in a crash landing that imperils the duo
Will goes up against the heads of the Sanctuary Network to defend Magnus who is charged with a shocking murder. But as the evidence stacks up against her, even Will has trouble finding a way to convincingly defend her innocence.
Henry tries to determine why a seemingly docile domesticated abnormal suddenly turned violent after it attacks a research scientist.
A confused Dr. Magnus finds the Sanctuary and surrounding city has been destroyed, but she has no idea how it happened. While searching the remains she is pounced on by a vicious creature, leading to two armed men rescuing her and taking her to a nearby abandoned building. After being hosed down and dumped in a room on her own Magnus becomes fearful when an aggressive man, with a familiar face, enters.