Arun Rath

Carfentanil is an opiate 10,000 times more powerful than morphine. And since last summer, it's been killing addicts and confounding first responders across the country.

When Harry Selker was working as a cardiologist in the 1970s, clot-busting drugs were showing great promise against heart attacks. But their lifesaving properties were very time sensitive. "If you give it within the first hour it has a 47 percent reduction of mortality; if you wait another hour, it has a 28 percent reduction; another hour, 23 percent. And people were taking about 90 minutes to make that decision," he recalls. "So they were losing the opportunity to save patients' lives."