First Daughter by Eric van Lustbader
When an accident takes the life of his daughter, Emma, ATF agent Jack McClure blames himself, numbing the pain by submerging himself in work. Then he receives a call from his old friend Edward Carson.
Carson is just weeks from taking the reins as President of the United States when his daughter, Alli, is kidnapped. Because Emma McClure was Alli's best friend, Carson turns to Jack, the one man he can trust to go to any lengths to find his daughter and bring her home safely.