The book starts at Sabriels school in the country of Ancelstierre, where she receives word of some calamity from her father, Abhorsen, via an undead creature. She then leaves for her father's house in the Old Kingdom where Ancelstierran technology falls apart and magic holds sway. Along the way she discovers that the Kingdom has fallen apart over the last 200 years with widespread sighting of the undead. Upon reaching her father's house, she is joined by Mogget, a Spirit in the form of a cat, bound to her family by its collar, which Sabriel is told never to remove. Using a magical flying craft, a Paperwing, they travel towards the former capital of the old Kingdom in search of Sabriel's father. Along the way they are attacked on the way by the dead, in order to save herself Sabriel removes Moggets collar.
He is revealed to be Free Magic elemental. And almost kills Sabriel, but she rebinds him with ring she had received from him whilst still bound. The two are now faced with another problem, they are stuck in the pit of holehallow, a place of burial for ancient royalty. Here they find a young man trapped in the form of a figurehead with his soul hidden, and preserved, in death. Following a rescue by Sabriel the young man, suffering from amnesia, joins their party. At Mogget's suggestion he is called Touchstone, the name of a Jester, he only agrees to this because he is ashamed of some action in his past.
The companions escape from the holehallow and continue on a journey to try and discover the Abhorsen. They soon find him, trapped in death, he is to far gone to be saved, but he tells Sabriel that an evil has gripped the land, a spirit known only as Kerrigor, formerly a royal prince, who intends to claim all of the Old Kingdom for the dead by using blood of the great magical families, such as the Royalty and Abhorsens, to break the great charter stones, powerful relics enforing human magic over the acidic free magic of monsters such as Mogget. The Abhorsen reveals that Kerrigor has preserved his living body somewhere and this prevents him from ever truly dying. He tasks Sabriel with destroying the body and ending Kerrigor's plans. Emerging from death for a last time, Sabriel's father magically delays Kerrigors releasing Mogget due to his powerful abilities, Sabriel spirts herself and touchstone as far away as possible.
This succeeds in returning Kerrigor to the land of the dead. Sabriel and touch stone use a paperwing, provided by another of the great families, the clayr, to bring them as close as the Paperwing can take them to Ancelstierre, then she and Touchstone set off to find Kerrigors body.
Upon finding it they also come across Kerrigor, after a tremendous battle Sabriel binds him using Mogget's old collar, but dies in the process, upon reaching the land of the dead she is saved by a host of former Abhorsen, who claims she must live at least until she finds a successor