the same day rhoni reuter was killed. >> reporter: rhoni didn't have enemies but gayle did?reporter: not only did they think the letters hads a direct connection to the murder but one was found in rhoni's purse the day she was killed. how big of a break does that seem? >> if she mailed the letter and rhoni had the letter, she knew her letter. >> reporter: does she sound jealous? >> yes. >> reporter: motive? >> yes. >> reporter: she was training one of her regular clients who happened to live in a town next to deerfield. her alibi seemed to check out. as soon as you talk to the client, is she crossed off the list? >> not immediately. we don't know their relationship, if he could be lying or not. >> reporter: another woman popped up on the radar from tipsters. >> three phone calls from people who gave this name. the information they were leaving is she would be an individual capable of doing something like this because of the relationship she had with shaun gayle. >> capable of this murder? >> yes. >> reporter: the plot, as they say, was thickened. >>> coming up, who is this?