The forecast called for record snowstorms, and Luis Octavio López Vega had no heat in his small hide-out.

Thieves had run off with the propane tanks on the camper that Mr. López had parked in the shadow of a towering grain elevator, near an abandoned industrial park. Rust had worn through the floor of his pickup truck, which he rarely dared to drive because he has neither a license nor insurance.. He had not worked in months and was down to his last $250.
Going to a shelter might have opened him to questions about his identity that he did not want to answer, and reaching out to his family might have put them at odds with the law.

“I cannot go on like this, living day to day and going nowhere,” Mr. López, 64, said one night last winter.
Mr. López, a native of Mexico, said in Spanish that he has lived under the radar in the western United States for more than a decade, camouflaging himself among the waves of immigrants who came across the border around the same time. Like so many of his compatriots, he works an assortment of low-wage jobs available to people without a green card. .
Mr. López played a leading role in what is widely considered the biggest drug-trafficking case in Mexican history. The episode — which inspired the 2000 movie “Traffic” — pitted the Mexican military against the United States Drug Enforcement Administration. Throughout the 1990s, Mr. López worked closely with them both. He served as a senior adviser to the powerful general who was appointed Mexico’s drug czar. And he was an informant for the D.E.A....