. >> reporter: and rye says kayla, and another american hostage, journalist steven sotloff, figured out a way to pass letters back and forth, creating a makeshift game of trivial pursuit. was it dangerous to be moving these letters back and forth? >> of course it was. >> reporter: but she did it. steven did it? >> yeah. if i've been by myself at her place, i would probably say, "no, no letters. it's too dangerous." >> reporter: back in arizona, kayla's parents held out hope that isis would treat an aid worker gently, that one of the humanitarian groups she was connected to would help negotiate her freedom. but that did not happen. >> no one would claim her, so they assumed she was a spy. and we found out that her fingernails had been pulled out. her hair had been shaved and that she had been tortured. >> and that was just one of the hardest days for me. >> reporter: and the prospect of a negotiated release grew increasingly unlikely as the muellers soon found themselves up against the u.s. policy against making concessions to terrorists. >> i firmly believe that the united states govern