>> announcer: tonight on all-new "20/20" -- no body. no weapon. but definitely a murder. >> this was a very quick -- and the frantic cleanup. >> announcer: just this week, a bombshell jailhouse confession that could change everything. what really happened to popular teenager brian carrick. who went to work and just vanished. >> it's every parent's worst nightmare. and i guess we're living it. >> announcer: is the right one behind bars? >> there's somebody who knows exactly what happened. >> announcer: the "20/20" exclusive with the man locked up for murder, out of shackles, out only to talk to us. tonight, we're taking you inside

a cold case and cold storage. >> what did you think that circular stain was from? >> announcer: those interrogation tapes. stock boys on the hot seat. and the blood-sniffing crusader who says she can name the real killer and can show what he did. tonight k you solve the mystery on johnsburg road. >> where did he go? here's david muir. good evening. tonight, here, a mystery in the heartland with an explosive new twist. a popular teenager who leaves the house to go to work across the street, at the town grocery store, but he never comes home. what really happened at the back of that store, in the storage cooler, a man behind bars but is he really the man who killed him? and you'll hear from someone else who said he lied to put him

there. all part of the mystery of johnsburg road. here's abc's ryan smith. >> reporter: the village of johnsburg, illinois, the essence of small-town america. a flag-waving heartland, some 50 miles outside of chicago. a conservative community where tradition reigns and nostalgia is embraced. some call this "mayberry of the midwest." >> there's a lot of farms out there, still. some subdivisions. you got the grocery store, bowling alley. very simple, very -- just kind of easy. >> reporter: but johnsburg is also a village with a secret. a lingering 12-year-old unsolved mystery that still has people talking. >> i really can't think of a bigger news story. >> i would say everybody had an opinion. >> i think there's somebody who knows exactly what happened.

>> reporter: what happened to brian carrick, a likable 17-year-old high school junior, who one friday night vanished from inside the grocery store where he worked as a stockboy. just five days before christmas. amanda marrazzo covered brian's disappearance for "the chicago tribune." >> he was excited about christmas, there was no indication for him to run away. >> reporter: his father william carrick, an electrician, says his youngest son was always by his side. >> wherever his dad went, his dad said he'd be in his hip pocket. he was an entrepreneur. sfwlr and he loved val's foods. the village's only grocery store directly across the street from the carrick home. >> you have no idea how smart he was. if you tell him to do one thing one time, say this is what i want you to do. next time, he'll tell you what to do.

>> so, he was a go-getter. >> if there were more people like brian in this country, there will be a beautiful future for america. >> reporter: in johnsburg, everyone knew the carricks. the hardworking irish catholic family with 14 children. brian was the 11th. >> the parents, when they got married said "god give us as many kids as you want to give us, and we'll take them." >> describe the carrick family for me, what were they like? >> all very nice people. one of the sisters said they didn't have the best clothes. and they didn't always have school supplies. but they had a lot of love. >> reporter: that december 20th was brian's day off. but went to val's looking for a co-worker, passing his brother eddie, also a stockboy, on the way. >> eddie was going out to get the carts from the parking lot and brian was walking into the store. he never saw his brother after that. >> reporter: the next day, his mother terry carrick received a troubling phone call. brian hadn't shown up for work. >> she knew her son would never miss work. that was his life was going to that store. >> reporter: she went upstairs he wasn't in bed.

she knew immediately something's wrong. within days johnsburg was reeling in disbelief. this was not the kind of town where people just went missing. >> johnsburg's so safe and such a small, family, church-oriented community and then to have something like this happen is just very hard to take in. >> reporter: supporters gathered at a vigil for brian. walking the same route he walked to work, across johnsburg road. his mother terry, the strong matriarch shaken. >> horror. the torture of not knowing where he is or what happened. that's every parent's worst nightmare and i guess we're living it. >> reporter: as weeks passed, no one knew if brian carrick was dead or alive. >> johnsburg police were involved. illinois state police became involved. the fbi became involved. people were searching the places where brian might go around town. they had the search dogs, they had -- psychics would come to

terry's front door, and try and tell her where he might be. >> reporter: val's foods posted a $25,000 reward. grocer jerry casciaro's daughters, julia and joanne. i think some people would say, "you're putting up $25,000 for somebody who works for them. not a family member but an employee." >> because, you know, the carricks needed it. they didn't have the money. we were desperate to try and find what happened to him. >> reporter: the carricks and the casciaro's, two of johnsburg's most well-known families. friendly for nearly 20 years. almost half of the carrick kids had worked at val's. i understand you have a picture of him in your wallet. >> yeah, definitely. >> reporter: can you show me? >> sure. >> reporter: so, this is some 12 years later -- >> this is a beautiful kid. >> reporter: -- you're still carrying this picture in your wallet. >> right. >> of this young man who worked with you as a stock boy. >> right.

right. >> reporter: high do you carry his picture with you? >> because, to me, he was like a son. >> reporter: an early break in the missing persons case revealed blood evidence in and around the grocery store produce cooler, news no one wanted to hear. drops, spatter, smears, a bloody fingerprint -- brian's blood. what heartbreaking mystery did the family's grocery store hold? what was your reaction when you heard that police found blood in the produce cooler? >> i think then immediately it's like, "well, who did it?" everybody was just like on edge. >> reporter: police quickly turned their attention to the one with no priors. the boss's son. 19-year-old mario. >> are you kidding me sf? >> reporter: you guys are shocked at that point? >> yes, completely shocked. >> mario is one of the nicest, kind, intelligent, funny, just a sweetheart. >> reporter: cops were being to

develop a more sinister profile. >> allegedly was selling dope and i think he coerced my son into working for him and somehow, yeah, things got out of hand. >> there were rumors that there were some things going on at the grocery store. tell me that theory. >> reporter: he would use some of the kids from the grocery store to sell the drugs, brian carrick. and brian carrick, bein' the sweet kid that he is, wouldn't always collect the money. >> reporter: authorities were convinced that the boy who freely gave away pot was a victim of foul play. they believed he was killed over a drug debt he owed mario. the police began to dig into mario. they believed that he was selling drugs. >> i think you know maybe he

smoked pot. i think maybe he and his friends bought and sold it to each other. we're talking about a very small amount. >> reporter: but with no eyewitnesses, no physical evidence tying mario to the crime scene or even a body, the investigation grew cold. and so did the bond between the carricks and the casciaros. >> the relationship had gone sour. and then one day my dad said that mrs. carrick had come in the store and she kind of turned her back to him when he approached her to say hello, and that was the last time she ever spoke to him. >> reporter: but for mario, life was moving on. here he is receiving his degree in finance from illinois state university, three years after brian's disappearance. >> yeah! >> reporter: but for the carricks, no closer to any answers. it was as if time stood still. mario joined the family grocery, worked as a manager, and helped build the business.

>> that was not the only store that he was going to have. it was always going to be two stores, and three stores and four stores. >> reporter: that grand plan would never happen. mario's world was about to collapse around him. a break in the case. this stock boy, shane lamb, would change everything with a tale of violence in the produce cooler the night brian carrick vanished. >> i hit brian a few times. he was bleeding from his mouth. thought i knocked him out. >> where's mario when you're doing this? >> right in the doorway. >> reporter: what did happen to brian carrick? stay with us "i'm 16 and just got my first car" feeling. presenting the buypower card from capital one. redeem earnings toward part or even all of a new chevrolet, buick, gmc or cadillac - with no limits. so every time you use it, you're not just shopping for goods. you're shopping for something great.

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>> announcer: "20/20" continues, once again, ryan smith. i would like to thank everybody for attending tonight. a toast to prosperity and the future. salud. >> reporter: happy memories for mario and the casciaro clan. older brother eugene's big italian wedding. but good times were in short supply for this family. jerry and maria casciaro, italian immigrants, met and married in the states, realizing

their american dream when they joined with relatives to buy val's foods. >> you know, he didn't have anything given to him. he came to this country, built what he had from the ground up. >> reporter: in an age of superstores, val's thrived in the small town where a night out is spent at a local sports bar or bowling alley or a pizzeria. nearly every family in the