Nemesis. The Ryan Mitchell Thrillers, #6

When a brutal terrorist attack maims dozens and kills someone close to Ryan Mitchell, he decides to take the law into his own hands and sets out to kill whoever was responsible. He, however, learns things are not as they appear. Before long, Mitchell and his friends are dragged into a deadly struggle with a foe from the past and a man who has waited decades to settle an old score. From Greenland to Zimbabwe, to Libya and Russia, the clock is counting down toward Armageddon.