thumbprints and signatures. except for the "s" in hawks where jackie signed. both times the letter is written in by someone else. why would jackie forget the "s" on her own name? was it a mistake? or was it a message that she hadn't signed that document willingly? there was no way to know. and then, in response to all that tv coverage -- >> the couple's silver honda crv with arizona plates is also missing. >> -- a tip that would change the direction of the case. >> we get a telephone call from an american citizen in mexico, and this person calls up and says i'm looking at the vehicle right now. it's parked in a driveway in mexico. >> at that point that was the biggest break you got? >> absolutely. >> december 16th, 2004. a month and a day after tom and jackie were last seen, detective byington headed to mexico, hoping to find not only their car, but some answers, and maybe them. >> i'm thinking tom and jackie hawks are hiding out in mexico.