Still no Title

My WIP is done - sent off to crit partners - will need about 3,000 more words to it, I think, to really make it perfect. But I had to write 'The End' on it, as I got another job for 8 drawings for a polo book.
But my book still has no title!
This is the first time I've finished a book and still had no name for it. Usually I come up with something before typing 'The End'.
The first book in the series is called 'Jack's Back' (working title, but I really like it and hope it stays)
This story is about May, the vampire killer. She's small, smart, and deadly, and she takes life very seriously having been killed once before by a mob of rogue vamps. She's MUCI's(*Mutant and Undead Criminal Investigation*) best man, er, woman, for catching and killing rogue vampires, so when two kids show up with all the signs of having been killed by a rogue, May gets the case. Clues lead straight to a certain Bartholomew Aelfrith, a vampire, whose sense of humor and tall blond good looks are enough to convince May he needs killing...even if he's not the killer. If he makes one more joke about her chop-sticks, she's going to stab him through the heart with one. The problem is, Bartholomew is probably the only person who can catch the real killer, so May has to put up with his insouciance and his wise-cracks...and his penchant for picking up strays of all kinds. But if he says, "I've got a plan" one more time, she's going to scream.

Any ideas at all for a title?????

I'm open to suggestions!