BUCKEYE, Ariz. _ Melissa and Daryl McKinsey first heard about "Mexican Oxy" last year when their 19-year-old son Parker called in tears.
"I need to go to rehab," he said.
Several months earlier, a friend had given Parker a baby-blue pill that was stamped on one side with the letter M.
It resembled a well-known brand of oxycodone, the prescription painkiller that sparked the American opioid epidemic.
But the pill was actually a far more powerful and more addictive opioid: fentanyl.
Within weeks, Parker was crushing and freebasing up to eight pills a day.
Developed decades ago as a painkiller of last resort, fentanyl has surpassed heroin and prescription pills to become the leading driver of the opioid crisis and is now the top cause of U.S. overdose deaths.
Last year, more than 31,000 people in the United States died after taking fentanyl or one of its close chemical relatives, according to the U.S. Centers for Disease Control and Prevention. No other drug in modern history has killed more people in a year.
Fentanyl started appearing on U.S. streets in significant quantities in 2013, most of it produced in China and shipped in the mail.
Today, officials say the majority is smuggled from Mexico, where it is remaking the drug trade as traffickers embrace it over heroin, which is more difficult and expensive to produce.
While heroin is made from poppy plants that grow only in specific climates and take months to cultivate, fentanyl and other so-called synthetics are cooked from chemicals in makeshift laboratories in a matter of hours.
U.S. border agents have been intercepting increasing amounts of fentanyl. In January, they reported their largest seizure ever: 254 pounds of powder and pills hidden in a truck carrying cucumbers into Nogales, Ariz.
Parker McKinsey grew up 200 miles north of there, in the idyllic Phoenix suburb of Buckeye. American flags and wind chimes hang from porches, and traffic is so light that residents sometimes drive golf carts on the streets.
His parents raised him and his younger brother Bryan to believe in two things: God and baseball. Best friends, the boys were blond and blue-eyed and were both standout high school players, competing each summer in the nation's top club leagues.
Parker, who had a rebellious spirit and had struggled with school, was devastated when he failed to attract interest from college teams. After graduating in the spring of 2017, he fell into a depression, and slipped from smoking marijuana into stronger drugs.
It was Bryan who urged his parents to heed his older brother's plea for help.
"He could die," Bryan warned.
The McKinseys dug into their savings to enroll Parker in a $20,000-a-month rehab facility.
The morning they dropped him off, his mother, an elementary school principal, thought to herself: "This is the worst day of my life."
That day, however, was still to come. The culprit, again, would be a blue pill stamped with the letter M.
