Syd Moore 
Strange Tombs — An Essex Witch Museum Mystery [EPUB ebook] 

The fourth instalment in Syd Moore»s spooktacular witch detective series
Halloween in Essex and the Mystery and Suspense creative writing course at old Ratchette Hall is off to a satisfyingly creepy start. But things take a turn for the worse when the course administrator is discovered dead, clutching a marble finger to his chest. For why would anyone, undead or alive, want to kill mild-mannered Graham?
Luckily Rosie Strange and Sam Stone are on the case. Soon, however, they are digging up more questions than answers: who are the unearthly howls emanating from neighbouring Witch Wood every night? How has a stone crusader, on display in the church, managed to lose a finger? And, more sinister yet, why is one of the tombs missing a corpse?