Final Target

The fourth book in the Wind Dancer series by Iris Johansen. The story revolves around Melissa Riley, who arrives at her sister Jessica Riley's isolated Virginia country home to find herself plunged into a deadly drama. Jessica, a renowned psychiatrist, is attempting to draw the President's daughter, Cassie Andreas, out of a severe catatonic trauma.
The last thing Cassie saw was an organized team ruthlessly murdering her nanny and the Secret Service agents sworn to protect her. To free Cassie, Melissa and Jessica must trust a mysterious and charismatic man named Michael Travis, who made his fortune in the international underworld and claims to have saved Cassie during that traumatic night.
As Melissa and Jessica follow a dangerous plan to save Cassie, they are drawn into a world of treachery and danger, where they must confront a killer who will stop at nothing to achieve his goals.