Inside James Clapper's journey to free two Americans in North Korea

When Director of National Intelligence James Clapper traveled to North Korea to help secure the release of two Americans imprisoned there, he didn't know whether his mission would be a success.

"I was quite apprehensive, because we weren't sure how this was going to play out. I personally was not completely confident that we would actually, that they would actually release our two citizens, and so yes, it was apprehensive," Clapper said in an interview with CBS' "Face the Nation."

Clapper was picked for the job of negotiating the release when the North Koreans signaled that they wanted the U.S to send a high-ranking official. The fact that he wasn't a diplomat meant he could avoid any demands on that front. Plus, he told Bob Schieffer, North Korea has "always been on my professional bucket list."

He described his trip in detail, saying his arrival in the country was greeted by the Minister of State Security and a translator. He carried a letter from President Obama explaining that he was an envoy for the administration and said that it would be a positive gesture for the North Koreans to release the two Americans, Matthew Miller of Bakersfield, California, and Kenneth Bae of Lynnwood, Washington.

"I think they were disappointed, frankly, that I didn't have some breakthrough," Clapper said of the North Koreans. But, he added, "I did take a ray of optimism from the younger interlocutor who accompanied me on the way out to the airport, and I think it illustrates the potential here for the future. Because I do think there is a generational difference between the older part of the regime" and younger North Koreans.

He said the younger interlocutor "professed interest in more dialogue" and asked if he would be willing to come back to Pyongyang, which Clapper said he would.

Clapper met with the head of the Reconnaissance Guidance Bureau, which he said is a combination of intelligence and special operations forces. He described their dinner as "pretty terse."

"The country feels itself to be under siege. There is a certain institutional paranoia and that was certainly reflected in a lot of things that he said," Clapper said. "For example, allegations about our exercises that we conduct in the Republic of Korea. They did bring up the human rights issue at one point, although we were well into the dialogue, criticizing us for our interventionist approach, our interventionist policies into their internal matters...it wasn't exactly a pleasant dinner."

After a long wait, a government representative gave Clapper and his party 20 minutes to collect their luggage and leave. They were taken to a hotel in downtown Pyongyang, and then there was a procedure he described as an "amnesty-granting" ceremony.

Afterwards, Clapper said, the government representative said he hoped there would be more dialogue but not about the detainees. The two Americans changed clothes and then they flew home with Clapper.

When Schieffer asked if anything has changed in the relationship between the two countries, Clapper said "that remains to be seen."

"As to what, where do we go from here? Is this, will this perhaps serve as a catalyst, or stimulus for more dialogue? I hope so, but I don't know," he said.