Travis' brother has served multiple tours in Afghanistan and knows firsthand how heavy military-issued armor can be. So Travis decides to build his own version of a lightweight, full-body flak suit that could protect a soldier without limiting mobility. To put the design's mobility to the test, a retired drill sergeant puts Travis through civilian boot camp. Then, to prove the armor is light enough for a soldier to wear in combat, Travis straps on the suit and runs the full Marine Corps Marathon.