This collection contains both Shadows in the Water and Under the Bones. 

In Book 1, Shadows in the Water:
Meet Louie Thorne. They didn't kill her—and they'll soon regret it.
When DEA agent Jack Thorne's house is stormed by vengeful drug lords, both he and his wife are shot dead. Only his daughter Louie survives—by using a terrifying power that defies reason.
Piecing together a life in his absence, Louie embraces her gift and her rage under the force of a single need: revenge.
She will destroy the men that took her family. No matter the cost, no matter how many bullets, she won't stop until justice has been well and truly served.

In Book 2, Under the Bones:

Enemies make the best allies.  
Louie Thorne is good at only one thing. Killing. She knows peace only when she kills and this relentless thirst drives her to hunt the world's worst crime lords. But when her cancer-stricken aunt makes a dying wish, Louie is torn between her own dark nature and a promise made to the only family she has left.  
Enter Konstantine, bastard son of the crime lord who killed Louie's family, and now the leader of the Ravengers—a ruthless crime faction from Florence's underworld. He didn't rise to power without making enemies and now one of those enemies has made Konstantine the most hunted man alive. Konstantine's only hope of reclaiming his throne is to trust the woman who wants him dead...