>> reporter: four people familiar with the investigation tell nbc news that special counsel robert mueller is looking into whether ousted national security adviser michael flynn agreed to rough offer of $15 million for a quid pro quo with the government of turkey just weeks before donald trump's inauguration. under a microscope, an alleged meeting at this upscale new york restaurant blocks from transition office where flynn then advising the transition and turkish officialed allegedly discussed removing chief rival of turkey from the u.s. and sending him pack to turkey. lives in pennsylvania. ...