Cut Glass: Jewels - Diamond - Cut Glass, #1

Forget everything you think you know about mass murderers and crimes of passion, because now you're going to learn the truth. People don't decide one day to go out and kill as many people as they can, or wake up one morning, grab the nearest shotgun or axe, and proceed to hack apart their loved ones. They do it because they're infected with a jewel, a creature of intense beauty and danger. Once the jewel takes over a host's body, that person dies, leaving the jewel in total control to thrive on fear and horror.
Cutler Glass is a lapidary, one of an unknown group of people who've dedicated their lives to destroying jewels. But in order to keep the jewels from slaughtering innocent victims, she has to kill the host and then eat the jewel that emerges from the body. Except this time the jewel she's assigned to go after, a diamond, has infected a very wealthy and influential man who has hired police protection.
When Detective David Fellowes clashes with Cutler, it's going to take more than a simple explanation before he believes her outlandish tale. Until then, they both have to deal with their growing attraction to each other, and the fiery emotions it ignites.