Nicholas Sayre and the Creature in the Case is a short story entry in the Old Kingdom series by Garth Nix. A follow-up to Abhorsen, it tells of Nicholas Sayre's encounter with a Free magic creature in Ancelstierre and his return to the Old Kingdom. Published initially as a stand-alone story for World Book Day, it was later released as part of Nix's short story anthology Across the Wall: A Tale of the Abhorsen and Other Stories.
Nicholas Sayre is sent by his Uncle Edward to a party at Dorrance Hall to observe the workings of a clandestine government organisation responsible for gathering information about the Old Kingdom. The organisation's head, Alastor Dorrance has covertly obtained a Hrule that has been telepathically contacting him since his childhood, and intends to free it across the Wall. Dorrance intends to feed the creature Nick's blood; however his blood is too strong for it and it runs amok. After the creature rages out of control and runs north, Nicholas gives chase. He catches up with it at the Perimeter and attempts to poison it with his blood. He passes out. When he awakens, Lirael is present, and defeats the creature with a thistle.