The book known as The Dischord Grimoire is an incredibly powerful tome, believed capable of altering the true passage of time itself. And the Doctor has it in the TARDIS.
Wanting to look into this mysterious opus further, he decides to take it to an old friend in The Recusary - a monastery-like retreat on a moon of Gallifrey.
But he’s chosen an inauspicious time to arrive. Something else is visiting the Recusary. And this something hasn’t brought a book with it... but death.
Note: This title is also available on CD as part of Doctor Who: The Fourth Doctor Adventures Series 11: Solo