In the Person of Interest episode S03E15, the POI was Sandra Nicholson, who works in a 911-dial in station. She was forced by a caller to delete calls from a certain date from the server.
At the end of the episode, the POI as well as the caller are alive. Finch gets a phone call from him that he will be after Finch
You, however, are another story entirely. Be seeing you.
Who was this caller? Was he ever mentioned after that? (Maybe I have missed something, but as of today's screened episodes, I have not seen him again).