The Deadstone Memorial, by Trevor Baxendale
This is one of those Who novels that could have made a good TV episode - indeed, it possibly did, with the central theme of children's nightmares becoming reality used twice that I can remember in New Who (Fear Her and Night Terrors). There's also a zombie character from the seventeenth century. It's solid stuff, well-written, giving the Doctor, companions Fitz and Trix, and the various incidental characters plenty to do and doing it interestingly.