There will indeed be a third book featuring Hallie Michaels and Boyd Davies.  It will be published in early 2014.

In the meantime, here’s a brief snippet (which could still change) from Strange Country:

The phone woke Hallie at 4:00 in the morning.

She blinked, sitting up before she was even awake, but disoriented because it was dark and she’d been having a dark dream that she didn’t actually remember, except it was about escape and wanting and things that had never been promised, but could still be taken.

“Hello?”  For a moment, she thought it was Death on the phone, thought he’d found a way to reach her in the world.

“Hallie Michaels?”

She didn’t recognize the voice, couldn’t have recognized it because it was mechanical, spoken through some sort of filter, deep and slow and flat like something ground from stone.

“Who the hell is this?”

“Is this Hallie Michaels?”

Hallie threw back the blankets, dropped her bare feet onto the cold wood floor and started looking for jeans and a shirt.  Nothing good was going to come from a disguised mechanical voice calling at four o’clock in the morning.