It Is What It Is. The Nate Thrower Series, #8

Thrower is hired by super wealthy businessman Thomas Sinclair, who's been receiving death threats. And it doesn't take Thrower long to use his skills to thwart off an attack. While Sinclair assumes the threats are because of some of his business interests, Thrower believes it may actually be due to a much deeper connection. One that may indicate someone in Sinclair's inner circle might be involved.
His wife, his assistant, everyone is a suspect in Thrower's mind. But no matter where the evidence leads, Thrower will make sure his client is protected at all costs.