genna? genna? >> one of the last people that she speaks with says that the phone goes dead. genna doesn't call back. her friend pages her a couple of times. genna never calls back. >> police found genna's diary in her bedroom which had an entry from the morning of her murder. >> dear journal, sorry i haven't written you, but i've been pretty busy. things have been going pretty good at school except for the fact that guys don't even know i'm alive half the time. >> the diary expressed a specific interest in two boys. one was considerably older than genna, a boy she met at a local amusement park. >> he was a young man, about 18 to 19 years old, who was preying on children that were not age appropriate. >> he was older than us. not -- not the best kind of person that you'd probably want to -- want to be with. but he -- there was something that she saw in him that attracted her to him. >> investigators needed to start checking alibis and there was one that almost defied belief. [ male announcer

saturday morning in 1995, as cathy mouser was leaving for work, she reminded her 14-year-old daughter, gennaat she was grounded for the weekend and wasn't allowed to use the tephon

. >> listen to genna, she's the master of facebook. come on, we're trying to get you 400 likes! >> "how to get 400 likes on your profile picture." a profile picture is kind of like how you want people to visualize you. you put your best foot forward. and your cover photo kind of tells about your personality. >> okay, guys, do you think darius should do this picture? >> that picture? as his profile picture? >> i vote no. >> rushkoff: what is it you would want the profile to accomplish? >> you want it to show the true darius, and usually when you think of darius, he's always smiling, always a happy guy to be around. >> oh, that's so cute! >> so it's this one? >> yeah, it's really cute. >> we found a photo of when he's smiling and being his true self. >> rushkoff: is it "true you" now? >> my profile is definitely the true me now. definitely true me. >> rushkoff: compared with the kids i met 13 years ago, this group seemed so sophisticated. >> what's your caption going to be? >> nothing... >> you need a caption! >> rushkoff: but as they sat there doing a virtual makeover on their fr