>>> a special eye to look at a crime scene and spot the thing that's out of place. the clue that will crack the case. in this story, that thing was so inconsequential looking no one even knew what it was, let alone what it meant. it took almost two decades, a team of determined investigators, and a detective with an unusual background to find out. here's keith morrison .

>>> it was the night before halloween , october 30th , late, midnight approaching. it happened in one of the middle class suburbs that sprawl across the los angeles basin . inside a fast food franchise closed for the night. a frantic scrabbling, running feet, then silence. the nice morning not far away, the hoinz family daughters prepared for a favorite celebration. kim was the eldest, then robin , trisha , and wendy . excited because this was halloween , one of the best days of the year.

>> oh, i loved it. we'd trick-or-treat and then sort the candy and trade what we liked.

>> a halloween morning long ago, it was 1984 . the morning after the incident at the fast food place. it started warm and sunny, that bubble of innocence. before anyone knew a thing. wendy donned her halloween costume , wore it to school as did trisha who wore hers to work. kim her eldest left early for her job at the nearby mall. robin wasn't home. after working late, she told her family, she had arranged to sleep over at a girlfriend's place. she was due home at any minute, as wendy remembers.

>> she was good about reporting in, telling us where she was going to be and when she was going to be home.

>> robin was 21 years old. she was a redhead, pretty, popular, friendly. she was an assistant manage her at a kentucky fried chicken franchise in the nearby town of torrance, had taken that late shift as a favor to a co-worker named sheryl .

>> i had asked robin if she would trade hours with me. i had just started dating somebody and we had plans.

>> so robin worked the late shift. she would close the restaurant, count the cash, carry it across the parking lot to the bank deposit box.

>> i knew robin was very cautious about, like, when i went to the store she would always tell me, make sure the door is locked.

>> this is not the sort of person who would have let someone in just anybody.

>> no, not at all.

>> so when sheryl arrived at work and pulled into the kfc parking lot --

>> i saw robin 's car. i thought, did she get mixed up, or did she think i wasn't trading it? why is she here?

>> sheryl crept through the empty kfc . everything seemed in order until she entered the kitchen.

>> as i came around the corner, i looked and i thought, why did robin spend the night here? that was my first reaction. and then when i looked closer, i saw that she didn't spend the night, that she had been killed.

>> she ran out of the place. someone called 911. detective jeff lancaster was among the first to arrive at the crime scene .

>> she was laying facedown. she had a pool of blood under one side. she had some slash marks through the left side of her face and neck injuries from a slashing type wound from a knife.

>> it didn't take lancaster long to figure out what happened. this was no accident.

>> she had two knife wounds to her back, the right side, lower area near the spine.

>> it looked, frankly, elementary. robin had been murdered in what appeared to be an attempted robbery.

>> the top cover of the safe was removed, and there were some paint chips missing off a new combination lock.

>> there were a few drops of blood on the safe, but no fingerprints, no murder weapon. but there was something rather odd lying near robin 's body.

>> it was just a piece of foam rubber . we kind of speculated that it came from some padding maybe for a backpack or a handle for a briefcase.

>> whatever it was and whenever it came from, the mysterious piece of foam wasn't much to go on. still, they bagged it, put it with all the other evidence. robin 's wallet told them who she was, where she lived, an officer went to the house to notify the family. no one home. he left a note which said, call the police department . it was something about robin .

>> so i called back. i said, is she all right? and he said, no, she's not.

>> so now kim , the eldest of the four daughters, had to reveal the news. she started with their mother.

>> the first words out of mouth were, you're lying to me. you're lying to me. because she couldn't believe that. once she realizes really i'm telling her the truth, we know we have to talk to my dad. we called him, and told him. he said, okay, we'll meet you at the house. then the whole domino thing of everyone that needs to know being told kind of started.

>> wendy , the youngest, heard at school that robin had been stabbed.

>> my immediate response was, did she die? because i want her to skill stil be alive, but she said no, she's dead.

>> trisha didn't hear a thing until she got home from work.

>> i had dressed up for halloween as well, and i was wearing robin 's flagster costume. and i look down and i see that i'm in her clothes, and i lost it. i was, like, get it off me. i mean, i was, like, screaming that i needed to be out of -- i just freaked out.

>> time doesn't wait, of course. darkness fell. halloween , laughing kids came to the door. the hoins sat in the dark and tried to get used to the idea of what grief feels like. policemen buzzed around the kfc all day, halloween day , for something to go on.

>> no signs of forced entry. she let somebody into the business. she knew the somebody and felt comfortable enough working on the paperwork while that person was in the business.

>> but who killed robin hoins, a former friend, a customer, a colleague from work? could it be that robin hoins had been murdered by someone she knew?

>>> coming up -- her co-worker, sheryl , remembers something.

>> he was going to come back and return his uniform.

>> who was "he"? and did he know anything about what happened to robin ? [ male