From Black Rooms. Number 4 in series

Natalie Lindstrom has finally left the underworld behind for a new career in the art world. But there's one world she can't escape: the Other world of the dead. As a former Violet, an elite crime-fighter with the power to channel murder victims, Natalie is now using her paranormal gift to summon the spirits of legendary painters. But she's about to discover how far some people will go to keep their hold on her - and others like her.
Evan Markham, her ex-lover-turned-Violet-killer, has escaped from prison and he's been made an offer he can't refuse: Natalie. But first he must help contact a deceased geneticist whose most intriguing experiment was brutally interrupted. To protect her young daughter and herself, Natalie must search for the scientist's only living test subject - a handsome but tortured artist who is caught in the grip of two opposing forces: one that wants his survival, another that wants him - and anyone connected with him - destroyed.