: Marcel is haunted by visions of Elijah and Klaus, who goad him to finally seize his revenge against the Mikaelson family for their centuries of betrayal.
Watch the official inside look for this episode to see the producers discuss the Hollow's psychological grip on Klaus and Marcel: [S4E5] I Hear You Knocking
The Hollow anchors itself to the living world by exploiting the darkest fears and past traumas of powerful supernatural beings. : Marcel is haunted by visions of Elijah
: Though the intended sacrifice failed, the Hollow accepts Marcel’s blood and grants his allies a magical thorn capable of killing an Original. [S4E5] I Hear You Knocking
The episode also marks a significant shift in the relationship between Freya Mikaelson and her captive-turned-ally, Keelin.