We'll start with more of my exclusive interview with Felix slater in the news because of his efforts to build a hotel in Moscow with Donald Trump. That's just one piece of an amazing story after being convicted of a felony assault, he began a secret life working behind the scenes with U.S. Intelligence agencies and investigators to take on Al Qaeda, Russian cybercrime, north Korean nukes and helped stop assassinationplots targeting Colin Powell and president bush. Mafia here in the United States. Yes. Al Qaeda. Yes. You gave the numbers of Osama bin laden. Yes. FBI agents and federal prosecutors who worked directly with him confirm his service on mob reeled and national security cases and former attorney general Loretta lynch testified that he provided information crucial to national security. You worked for the defense intelligence agency. Yes. You also worked for the CIA. Yes. You were an FBI informant. I was never an informant. I was a confidential source. I'm trying to tick through in my head your potential enemies. Al Qaeda, cosa nostra, Russian mob, Russian criminals. North Koreans. Aren't you scared? I've been scared every day of my life but courage is not the absence of fear. It's conquering it. Reporter: His government work connects him to key figures in the Mueller investigation. Andrew Weissmann supervised Sater's cooperation and Mueller himself was head of the F during the time Sater helped the government. Now Sater has talked to Mueller's team because of his business dealings with Donald Trump. I'm a businessman and, in fact, I was working on a bunch of real estate transactions, real estate deals to try to build some beautiful buildings with Donald Trump of all people. Back starting in 1996. Real estate I believe I started in '99. Donald Trump claimed he doesn't recall Sater saying in a 2013 deposition he couldn't even say what Sater looked like. If he were sitting in the room right now I really wouldn't know what he looked like. This is your business card then. That's my business card. He said he doesn't know who you are. Is he telling the truth. I'm sorry. I can't speak for the president. You worked with him for many years. Yes. Spoke with him, what, dozens of times. Hundreds of times. Yes. You say you can't speak for him but what does it feel like after all that Donald Trump says I don't think I could pick him out in a room. Disappointing. In fact, Sater says they were once so close in 2006 trump asked had him to look after don junior and ivanka while they were in Moscow and arranged for a private tour of Putin's office in the Kremlin. As we pass an office the security guard or -- I guess it was part of like the equivalent of their secret service says, that's the boss' office. And he opens the door just to show it sort of take a look through the door but don't go inside and ivanka said, do you think I could sit behind the chair? And he looked at me and says, okay, go ahead. I guess I convinced him and she sat down behind the desk. Spun twice in the chair, was very happy about it. Ivanka Trump told "The new York Times" she did not recall this incident but the deal now eyed by the special counsel is the one that didn't close. Trump tower Moscow. I approached Michael Cohen about the opportunity, very excited. Donald Trump signed the letter of intent. You had known Michael Cohen for a long time. We've known each other since we were teenagers. Some of the e-mails were made public published in "The new York Times." One said I will get Putin on the program and we will get Donald elected. Buddy, our boy can become president of the usa and we can engineer it. I will get all of Putin's team to buy in on this. Two guys that know each other since teenage years being beyond giddy that somebody that they knew and worked for was running for president trying to do a deal in Russia and clearly if the deal had gone a little further and I wished it would have, I would have gotten on the phone, I would have made phone calls. I would have gotten to people who know Putin to try to get his blessing and bring him on board and hopefully -- Help elect Donald Trump. I was trying to do a real estate transaction. I clearly was not involved in the campaign, nor was I involved in any of the political end. The times also wrote you wrote you were eager to show video clips to your Russian contacts of instances of trump praising Russia and the, quote, if he says it, we own this election. Yes, I wrote that. A lot of people have been wondering, is one of the reasons president trump was so easy on president Putin during the campaign is because he was looking to make this deal happen in Moscow. I can't speak for the president. I know that as a real estate developer, which is by its very nature three parts optimist, one part realist, to try to get a deal that is the tallest building in the world or the tallest building in Europe, you have to get buy-in from everyone. When you're doing all this were you aware at all of the Russian efforts to interfere in our presidential campaign? I was not aware of what they were doing. Most of it came out after the election and I read about it just like everyone else in the newspapers. I certainly would never in any way, shape or form work with people who are our geopolitical opponents to the detriment of our country. Do you think that anyone in trump's orbit was working with those people? I certainly hope not. But I do not know. You have spoken to Mueller's team, correct? I'm sorry. I can't answer something to do with any active investigations. If at the end of the investigation we discover that associates of president trump were actually working with the Russians as they were interfering in our election, what would be your reaction. Send him to jail. It's just incredible how much in the middle of this Felix Sater is. He worked with Andrew Weissmann, Robert Mueller was the head of the FBI. Obviously knows Donald Trump. And Michael Cohen and there's no question that Mueller is looking at this Moscow tower deal. To hear him say -- the president say he doesn't know who he is even though he, Sater, says they may have been together dozens or hundreds of times. Going back 20 years. It's really something. Michael.