While investigating the disturbing murder of two police officers, forensic psychiatrist Will Zimmerman meets a mysterious woman — Dr. Helen Magnus, who introduces him to a refuge for strange creatures.

As Will tries to reach the Sanctuary's newest resident, Ashley is confronted by John Druitt, a powerful and ruthess man from Helen Magnus's past, who is attempting to infiltrate the Sanctuary.

Magnus's team finds three sisters in stasis in a crypt, who Helen suspects are witches from the Middle Ages. But a deadly cabal comes looking for them.

While tracking an elusive jewel thief with the ability to contort his body through small spaces, the Sanctuary team uncovers an underground drug syndicate.

Helen and Will crash in the Himalayan mountains after capturing a vicious snow creature. But with rescue blocked by a major storm, their expedition members begin to lose their cool.

Helen and her team discover a pair of adorable little creatures and a vicious predator on board a ship whose crew were torn apart. Meanwhile, a young woman visits the Sanctuary and discovers she has special abilities.

Helen connects with an old friend in Rome, only to learn that he is being hunted by the Cabal. While Will investigates a bizarre incident at the Sanctuary, John Druitt abducts Ashley and reveals his history with her mother.

The Sanctuary is introduced to an artistically brilliant autistic savant after the young man's father kills himself. Henry struggles with the discovery that he is an abnormal.

Magnus and Will take a solitary submarine trip to investigate a problem with the Mer-people, only to find them all dead — victims of a parasite that infects Helen's brain and turns her against her friend.

The disappearance of a college friend leads Will to an underground fight club, where the Cabal is testing warriors before creating an army. Helen stumbles upon a man she is convinced is her father.

A television reporter and her cameraman infiltrate a warehouse where a super-powerful insect has brutally killed several people, and wind up following the Sanctuary team on their hunt.

After an outbreak of rash violence among abnormals, the survivors of the Five reunite with a plan to stop a Cabal threat by retrieving the last remaining Source blood.

Magnus and the others infiltrate an underground cavern in search of the Source, and must face a gauntlet of challenges tailored to their unique abilities. Meanwhile, the Cabal tries to turn Ashley against her mother, and to bring out Henry's animal side permanently.