The Janus Effect

When Paul Boland is eliminated from a poker tournament in Las Vegas, his opponent, Dr. Natalie Kelly, an ER physician at a nearby hospital, seeks him out afterwards to apologize for knocking him out. They become friends very quickly and despite the disparity in their ages end up in bed in Paul's luxurious hotel suite where, at the height of a magnificent orgasm, his old heart gives up on him. He dies with a wide smile on his face as it was the culmination of his dream to expire while making love to a beautiful young woman, which Natalie sure was. The strange thing, though, was that his mind survived the ordeal and implants itself in Natalie's brain, using her body as its host just before both fall into exhausted sleep.
The next morning, when both realize what had transpired and despite the bizarre occurrence, they are able to accept their strange new reality and explore the the reasons for it until they discover the cause of it in Paul's distant past. They also come to the conclusion that they will have look for another host for Paul's mind that will free him to live on his own.
Three days later, as their minds bond tightly in friendship, they find a suitable host, who happens to be a rogue FBI agent and serves as an executioner for the Al Qaida organization while masquerading as a hotel security supervisor, for which Paul has no compunction eliminating his mind and taking over his body.
Thus begins the great adventure....