Canadian Prime Minister Stephen Harper has arrived in Colombia to attend the Summit of the Americas, where the war on drugs and trade issues are expected to dominate the talks.

Much has been made of the risks Mexico's drug war poses to tourists, but the most immediate threat is to Mexicans themselves, who are having to share their cities with criminal cartels. As part of a weeklong series on the effects of the Mexican drug war, CBC News traveled to the increasingly dangerous city of Monterrey.