matter of at least a couple of days, trying to get him to contact her because he's so close to cathy and she's missing. >> reporter: montgomery noted a key detail about those pages. mary's home phone and cathy's home phone are the same number. >> they're the same numbers. >> reporter: so, seeing that number on his pager, how did sam know it wasn't cathy? >> if he knew she was alive, he would know he got 20 or 25 pages from cathy, or at least think that. if he's guilty and he killed cathy, he knows those 20 or 25 pages were not from cathy. >> reporter: that was tell number two. then montgomery noticed how, in his second interview, sam referred to cathy's murder. >> you know? but then this happened and -- shoot. >> he doesn't use the word "murder," doesn't say anything like that. it's like, "this happened," as if it's small. it's not that big of a deal, it's not horrendous.