Dark Descent (Dark, #9.5)

Dark Descent tells the story of Joie Sanders, a bodyguard, and Traian Trigovise, an ancient hunter, meeting after a battle in a deep cave filled with mystery and wonder. Set in the Carpathian Mountains, Joie, with her brother and sister go caving and come across the ancient warrior beset upon by several vampires. They have no choice but to throw their lot in with the hunter and do their best to escape with their lives from the underground labyrinth filled with ancient traps left behind by a powerful race.

Originally included the anthology "The Only One." Expanded version released in the 2 book volume Dark Nights.