A Friend in the Dark (Hazard and Somerset Book 10) by Gregory Ashe

When New York City confidential informant Rufus O'Callaghan arrives for a meeting only to find his police handler dead, he is suddenly thrust into a deadly game of survival. Meanwhile, former soldier Sam Auden investigates the suspicious suicide of his own police detective friend. As Rufus and Sam converge on the truth, they tumble into a treacherous web of lies, cover-ups, and mounting danger. With time running out, these two unlikely allies must uncover who is pulling the strings before they become the next victims.