Dark Horse by Gregg Hurwitz

Can you remain a good man when you help a bad one? . . .

Former government assassin Orphan X, Evan Smoak broke free to use his skills to help the good but powerless. But what if the person asking for help is neither?

When the daughter of a Texan crime boss is kidnapped by a ruthless drugs cartel, he asks Evan to rescue her.

The girl is innocent of her father's crimes.

But in taking the case is Evan crossing a line?

To find out he must break into an impregnable Mexican fortress.

Then somehow get her out alive . . .