On August 21, 2015, Ayoub al-Khazzani boarded the 15:17 train in Brussels, bound for Paris. Khazzani's mission was clear: he had an AK-47, a pistol, a box cutter, and enough ammunition to obliterate every passenger on the crowded train. Slipping into the bathroom in secret, he armed his weapons and prepared to launch his attack. But when he emerged, he encountered something he hadn't anticipated: three Americans who refused to give in to fear. Anthony Sadler, Alek Skarlatos, and Spencer Stone were childhood friends, taking a vacation together. They had some relevant training: Stone is a martial arts enthusiast and Airman First Class in the US Air Force; Skarlatos is an active duty member of the Oregon National Guard; and not one of the three was afraid of a fight. But their decision -- to charge the gunman, then overpower him even as he turned first his gun, then his knife, on Stone -- would never have happened if they hadn't had a lifetime of trust, support, and loyalty between them. This book is the gripping, true story of a terrorist attack that would have killed more than 500 people if not for their actions, but it is also the story of three American boys and their friendship.