As per Publisher's Lunch:
THEODOSIA and NATHANIEL FLUDD author R. L. LaFevers' trio of YA romantic historical fantasies focusing on teen girl assassins in 15th century France--starting with DARK MERCY in spring 2012 and followed by DARK JUSTICE and DARK HOPE in spring 2013 and spring 2014--each focusing on a different assassin trained at a convent serving the god of death himself, to Kate O'Sullivan at Houghton Mifflin Harcourt, in a preempt, in a good deal, by Erin Murphy of Erin Murphy Literary Agency (NA). Rights People represents foreign and translation.
A few more story details from the Publisher's Weekly Bookshelf:
In Dark Mercy, scheduled for spring 2012, Ismae learns she was sired by the god of death, is trained as an assassin, and is sent to court as a spy, where she must choose between serving her dark god and opening her heart to love. Companion novels Dark Justice and Dark Hope, each focusing on a different assassin from the convent, will publish in spring 2013 and spring 2014.
For those of you who stop by my blog regularly, THIS is the Secret Project I've been working on in between other books over the last couple of years. No, that's not true. I've been working on it off and on for over four years. It combines all of my favorite things; dark gods, dark choices, yearning, sneaking, epic romance. And how lucky am I to be working with The Best Editor EVER again. It's definitely one of those Pinch Me! moments in my life.