Simple Genius by David Baldacci
Michelle Maxwell is in trouble. Still reeling from the emotional turmoil of their last case, Michelle needs help from a professional. Sean King is willing to do whatever it takes to save her from herself and spends all of their agencies money to do so. he is forced to take a case from his ex, Joan Dillinger. It seems like a simple enough investigation. Head down to Virginia and figure out if Monk Turing, genius extraordinaire, was murdered or committed suicide. However, once Sean arrives at the think tanks compound, he is quickly cut off at every turn, secrets and soldiers are every where and he is forced to go head to head with the all-powerful CIA.
This is the third book in the Maxwell/King series. I love these two characters and also really enjoyed the introduction of Horatio Barnes and hope to see him in future books.