>> he related to us how lou castro and the others had moved to a residence in columbia, tennessee. we were reluctant to talk to his girlfriend because, again, we did not want to tip off lou castro or anybody else. >> reporter: and daniel, their inside man, delivered the mother load. 4 >> they'd bring me pictures, "do you -- can you identify these people?" >> they're out at the gate lookin', you know, surveilling, watching cars come and go. but you're able to put the picture together for them? >> correct. >> reporter: armed with daniel's email and his intel, goodwyn, snyder and sullivan got an official green light to pursue castro and try to take him out of business. and, castro, walking into a bank in tennessee, was about to make a big mistake. >> coming up, investigators finally get inside the doors of the commune.