She had been hunting him for a year, stalking him online, interrogating the criminals he worked with, even befriending unwitting relatives for tips on his whereabouts. Now she finally had one — a widow called to tell her that he was peddling flowers on the border.

Ever since 2014, she had been tracking the people responsible for the kidnapping and murder of her 20-year-old daughter, Karen. Half of them were already in prison, not because the authorities had cracked the case, but because she had pursued them on her own, with a meticulous abandon.

She cut her hair, dyed it and disguised herself as a pollster, a health worker and an election official to get their names and addresses. She invented excuses to meet their families, unsuspecting grandmothers and cousins who gave her details, however small. She wrote everything down and stuffed it into her black computer bag, building her investigation and tracking them down, one by one.

She knew their habits, friends, hometowns, childhoods. She knew the florist had sold flowers on the street before joining the Zeta cartel and getting involved in her daughter’s kidnapping.