FRONTLINE's primetime monthly newsmagazine returns with three new stories, leading with a timely report from the frontlines of marijuana legalization in California. The bulk of the marijuana consumed in the United States used to come across the border from Mexico, Canada and elsewhere. Now, more than half of it is believed to be home grown in California, where an enormous black market has emerged under the cover of the state's medical marijuana law. With more than a third of all states now experimenting with some form of legalization and decriminalization -- and several California counties attempting to openly regulate pot production -- FRONTLINE and The Center for Investigative Reporting team up to investigate the country's oldest, largest, and most wide-open marijuana market. Is the federal government now moving to shut it down? Also this hour: New Yorker writer and surgeon Atul Gawande reports on a doctor in Camden, New Jersey, who actually seeks out the community's sickest -- and most expensive -- patients. Dr. Jeffrey Brenner and his team are pioneering a practice called "hotspotting," in which medical care is focused on the hardest-to-treat to improve their health and dramatically reduce costs.