When does The Blacklist return?

The Blacklist is an American crime thriller television series that premiered on NBC on September 23, 2013. The show follows Raymond "Red" Reddington, an ex-US Naval Intelligence officer who had disappeared twenty years earlier to become one of the FBI's Ten Most Wanted Fugitives. Reddington surrenders himself to the FBI on two conditions: immunity from prosecution and cooperation with FBI criminal profiler Elizabeth Keen. Each season has received positive reviews, with many critics praising Spader's performance in particular.
Raymond "Red" Reddington is an ex-U.S. Naval Intelligence officer who had disappeared twenty years earlier to become one of the FBI's Ten Most Wanted Fugitives. He surrenders himself to FBI Assistant Director Harold Cooper at the J. Edgar Hoover Building in Washington, D.C. Reddington claims he wishes to help the FBI track down and apprehend the criminals and terrorists he spent the last twenty years associating with. Reddington offers Cooper his knowledge and assistance on two conditions: immunity from prosecution, and that he wants to work exclusively with Elizabeth Keen, a rookie profiler.