The newest promo for the “Deals With Our Devils” episode begins with a shot of Holden Radcliffe (John Hannah) flipping through the Darkhold (a.k.a. The Book of Sins). "Do not open that book," Mack warns. "You don't know the consequences." We then see Mack on a motorcycle and taking off in a huff. Agent Simmons inspects the husk of an unknown human in mid-Terrigenesis.