[s4e5]: I Hear You Knocking

: Freya risks her life to create a cure for the infection the Hollow placed on Klaus, solidifying her bond with Keelin as they work together to protect the family. Key Revelations

: Hayley discovers that her parents were murdered by Mary’s husband while he was under the influence of the Hollow. [S4E5] I Hear You Knocking

Watch the official inside look for this episode to see the producers discuss the Hollow's psychological grip on Klaus and Marcel: : Freya risks her life to create a

The Hollow anchors itself to the living world by exploiting the darkest fears and past traumas of powerful supernatural beings. [S4E5] I Hear You Knocking