Burning Water: Diana Tregarde Investigation Series, Book 1 / Mercedes Lackey

Dallas Police Detective Mark Valdez isn't just any cop, he's a psychic who knows that the cattle mutilations and torture murders he's been investigating are somehow tied together. He also knows that his meager psychic abilities aren't enough to identify the killers, much less stop them.

Luckily, Mark has an ace up his sleeve: an attractive young romance novelist who happens to be a practicing witch. And not just any witch, either - Diana Tregarde is a Guardian, charged with protecting the Earth and all its creatures.

Using modern science and ancient magics, Diana and Mark discover that they are tailing no ordinary serial killer but the awakened avatar of an Aztec god. Tezcatlipoca and his four beautiful handmaidens are preparing for a great sacrifice that will transform North America into a new Aztec realm.

Diana isn't sure her powers are strong enough to take on those of a risen Aztec god, but she has no choice. As a Guardian, she is sworn to protect mankind, even at the cost of her own life. Luckily, she does not stand alone. Mark Valdez is more than just a cop. And Tezcatlipoca is not the only Aztec god walking in the world.