Tom Kiefer was a Customs and Border Protection janitor for almost four years before he took a good look inside the trash. Every day at work—at the C.B.P. processing center in Ajo, Arizona, less than fifty miles from the border with Mexico—he would throw away bags full of items confiscated from undocumented migrants apprehended in the desert. One day in 2007, he was rummaging through these bags looking for packaged food, which he’d received permission to donate to a local pantry. In the process, he also noticed toothbrushes, rosaries, pocket Bibles, water bottles, keys, shoelaces, razors, mix CDs, condoms, contraceptive pills, sunglasses, keys: a vibrant, startling testament to the lives of those who had been detained or deported. Without telling anyone, Kiefer began collecting the items, stashing them in sorted piles in the garages of friends.