Mercy O'Connor is part of the staff of the Antiquities Department at Miskatonic University. For over a hundred years, men who called the Antiquities Department home have protected humanity from cultists in Dunwich, Massachusetts who want to summon unspeakable beings of tremendous power who would destroy us and everything we know. Mercy is not interested in taking part in this fight. She just wants to learn a few formula and sell enough of it to pay off her student loans—-and have another drink.
Unfortunately for Mercy, this Halloween (or Hallow Mass, as they say in Dunwich), the stars are right, and the cultists are determined to recover their Necronomicon held in the Antiquities Department's Special Collection so they can summon their gods. This time, the cultists have allies in the politically correct faculty and empty-headed "activist" students of the rest of Miskatonic University.
Now, Mercy O'Connor, Conrad Morgan, and security guard Joseph Bongani must face off against lunatics determined to devour our souls and see the entire world descend into madness and despair . . . and the Dunwich cultists too.
Hallow Mass contains examples of:
- Body Horror: Chester Sawyer, victims of various malicious formula
- Corrupt Bureaucrat: Armand Deale
- Eldritch Abomination
- Go Mad from the Revelation: The eventual fate of Aubrey Klumm-Weebner.
- I Just Want to Be Normal: Mercy OConnor really doesnt want to be one of the last defenders of mankind against the monstrosities summoned at Dunwich. What she really wants is to have another drink, make some money off of selling formula, and possibly land a decent boyfriend. Circumstances dictate otherwise, however.
- I'm Melting!: Upon his death, Chester Sawyer melts into a pile of goo.
- Magic by Any Other Name: Nobody does magic. The cultists and the Antiquities Department enact various formulas.
- Political Correctness Gone Mad: A significant part of the book is satire on politically-correct academia. Also, given that this is a Lovecraftian story, it is more literally true than usual.
- Teethclenched Teamwork: Almost all of the cultists viscerally hate one another. The faculty of Miskatonic, while nominally on the Dunwichers side, clearly look down on them. In return, the Dunwichers despise the Miskatonic faculty as weak and ineffective.