notorious prisons operated by assad. thousands of people deemed enemies of the previous regime were held tortured in those prisons. many have disappeared. cnn's clarissa ward visited one facility and made an incredible discovery. here's her report. >> deep in the belly of the regime's air force intelligence headquarters. these are english letters. we are hoping to find traces of austin tice, an american journalist held captive in syria since 2012. it's one of many secret prisons across the city. this specific branch was tasked with surveillance, arrest and killing of all regime critics. >> these are all cleaned out. >> we don't find any hints of ties, but come across something extraordinary. >> i can't tell, though. it might just be a blanket, but it's the only cell that's locked. >> is he going to shoot it? >> the guard makes us turn the camera off while he shoots the lock off the cell door brace up we go in to get a closer look. it's still not clear if there is something under the...