up our affidavit for the fisa court. >> the foreign intelligence surveillance act allows national security organizations to conduct surveillance to detect foreign governments spying on the united states or committing terrorism. it's a court, much like criminal court. so in order to get the ability to monitor somebody's telephone, you have to have a warrant. and in it, it explains that i believe chi mak is committing espionage for the following reasons. >> after five months on the case, we got authorization to tap his telephone lines. and to go inside of his house and do a covert search. we were listening to every phone call that came in out of that house. >> which led us to learn about a trip he was taking to alaska. >> when we found out chi mak and rebecca were going to alaska, i believe the first thought in everybody's mind was, he must be going operational. potentially meeting a handler to