The Fourth Perimeter

 Former Secret Service agent turned successful entrepreneur Kurt Ford thought he had suffered his share of tragedy when his adored wife died, leaving him to raise their young son alone.
But years later, his beloved son - also a Secret Service agent - turns up dead, and Ford is inconsolable. Refusing to accept the government's story that his son committed suicide, Ford investigates the case as a murder.
After learning from a Secret Service friend that two other young agents have also recently met with unusual deaths, Ford discovers that all three men were involved in a cryptic meeting with the President.
Now, faced with the possibility that this meeting was the cause of his son's death, Kurt Ford will attempt to do what only four other men in history have been able to accomplish - kill the President of the United States.