into this story for us. what are you finding out? reporter: learning more, wolf, about the intense pressure within the cia in weeks after 9/11. officials had to do something, anything to stop another attack. there came a moment when one of the biggest controversies of the war on terror was dropped in one attorney s lap. in the weeks after 9/11, the biggest fear gripping the nation was another attack around the corner. inside the cia, an obsession. to prevent another catastrophic attack on the homeland. reporter: john rizzo was one of the cia s top lawyers. how would the agency find out if another attack was coming? the cia worried one al qaeda operative in their custody could tell them. abu zubaydah, but he wasn t talking. in his new book rizzo writes one of the methods they wanted to try on him, waterboarding. depicted in the movie zero dark thirty. that wasn t the only enhanced interrogation technique they wanted to try.