On an expedition to Aconcagua 6,961 m (22,838 ft), Argentina in 2007, Agnew was part of a team led by Jon Muir when it became apparent that Muir had succumbed to altitude sickness and couldn't continue to guide the team. At high camp, the famed Viento Blanco (white wind) caused all climbing teams at height to attempt an evacuation. One of Agnew's fellow team members experienced life-threatening High-Altitude Pulmonary Edema (HAPE), needing immediate evacuation down the mountain and subsequently airlifted to Mendoza hospital. Agnew was left to lead the remaining team member's survival throughout a deadly night (including a tent fire and a death close by) at high camp. The retreat down the mountain the next day was memorable to Aconcagua's base camp which was also devastated and many teams lost the majority of their equipment.