Contract to kill - Andrew Peterson

When Toby Haynes witnesses a double murder-and suspects his boss, Tanner Mason, as the perpetrator of the crime-he does the only thing he can think of: he calls in Nathan McBride.

CIA special ops veteran McBride and his partner, Harvey Fontana, respond to their friend's plea. As they launch a covert investigation into Mason, the security chief for one of the nation's leading private military contractors, they discover that not everything is as it appears. Mason and his inner circle are leading a top-secret operation to tackle a wave of crime plaguing the US-Mexican border, and the murder may have been part of their complicated strategy-or part of a more menacing agenda. Soon McBride and Fontana find themselves engaged in a deadly game. With a powerful politician behind it all, stopping Mason could mean joining a secret war-with truly global stakes.