As England prepares to take on Mexico in the Fifa World Cup, another battle is playing out just beyond the Azteca Stadium. More than 130,000 people have been forcibly disappeared in Mexico as cartel violence surges, leaving thousands of families searching for answers. They say the authorities have failed them and are demanding justice. The Guardian follows two families as they confront the police and challenge the government, determined to use football's biggest tournament to expose Mexico's disappearance crisis.