Transcript for Birthday Sleepover Ends with 12-Year-Old Close to Death
And tonight here, our journey with one courageous family, one brave 12-year-old girl. For the first time, her parents are talking and you will meet 12-year-old Peyton. She some how crawled out of woods and wanted to live. Her paints want us to see the beautiful smile, a smile ha is just beginning to return. And they hope we can some how begin a conversation tonight, convinced there is a reason she survived. It's a Friday night in an American town, waukesha, Wisconsin and a mother and father like so many parents across this country are sending their daughter on a sleepover. Peyton leutner is 12, and they know her friend well, Morgan geyser another 12-year-old girl celebrating her birthday. Why would this night be any different, but it was. On Saturday may 31, 2014 a 12-year-old girl was stabbed -- Reporter: You're about to go inside a case that horrified this country. Two 12-year-old girls charged with viciously attacking their friend. She was stabbed 19 times. Reporter: Parents everywhere saying this could have been my child. An ordinary slumber party. Three girls and someone else. An unknown figure getting into that party too. A fictional character from the internet named slender man, who so many parents had never even heard of. We have spent months in that town and tonight for the first time, you're about to hear from that little girl's family. She was forced to go into the woods. Into the woods. Reporter: From the hero who found her at the edge of the woods. She was laying right here. Reporter: The doctors who saw how close to death she came -- The knife cut through the tissue. Reporter: And the school where just this month where they were all hoping she'd come back. One family's stunning journey about to play out tonight right before your eyes. It was a Friday night, right? It was a Friday night. Reporter: Their daughter Peyton had been looking forward to it for weeks. You remember how excited she was that Friday afternoon? Oh, my gosh, she was so, so excited. She squealed and jumped up and down. Reporter: Excited when her mother told her she could go to her sleepover early. Picked up even earlier than she thought? Picked up even earlier than she was expecting. She was so excited. Reporter: And had she gone on sleepovers before? Oh, yeah. And the -- this was just -- you know, her best friend's birthday party. It was just another Friday night. And they were talking' about it for weeks, if not -- And they were gonna go skating? They were gonna go to state -- Peyton loves skateland. So she was gonna go roller-skating, have some pizza, and spend the night at her best friend's house? Yep, they were probably gonna watch a movie. And so you thought this was -- And play American girl. Peyton brought her American girl doll with her. She brought her American girl. Reporter: But Peyton would not come home the next morning. Do you think Peyton had any idea? No. She had absolutely no idea. No. What she was walking into? She was blindsided. Reporter: Her parents blind-sided too. Friday night they send their daughter off. Saturday morning, mom is in the backyard. Joe was at work and I heard the doorbell ring and the dog bark. And it was a Saturday morning at, like, 9:30, 9:45 and around the side of the house, up over the deck came a uniformed officer. She had a badge and a gun. And -- they walked around the back of the desk -- the deck, asked, you know, "Are you Peyton's mom?" The first thing that goes through my mind is something has happened to somebody that I love. Because that's the only a uniformed officer and a detective comes to your house on a Saturday morning. Reporter: She would slowly begin to piece together what had happened -- in the 16 hours since Peyton had left for that sleepover. It is unthinkable. The first moment anyone would begin to learn of that horror was this call to 9-1-1. 911. I'm transferring a color on, big bend. Reporter: After she'd crawled out of the woods. And just listen at first the operators cannot believe what they were hearing. He came upon a 12-year-old female. She appears to be stabbed. She appears to be what? Stabbed. Stabbed? Correct. Reporter: Greg Steinberg was riding his bike that morning. On a path that had actually been chained off. It was pure chance that he came this way. Sir, are you with her right now? Yes. Is she awake. She's awake. Is there any bleeding going on? Her clothing has got blood on it. Okay and you found her and she was just laying there? Yeah. Reporter: Paramedics racing to the scene. And listen. The operator is still fearing that that 12-year-old could still be in danger. Is there any assailant around? Uh, I don't see anybody. Let me know immediately if you see anything else suspicious in the area. A car, or a person, anything. Keep your eyes open. Reporter: On that call, you can actually hear Greg comforting petyon. Honey, he's coming. They'll be here any minute. Who did that to you? And you were biking by, and she says to you what? "Could you help me please, I've been stabbed multiple times." I quick got out my cell phone I was shaking, and dialed 911, I just stayed with the 911 operator and I offered her water, because I had a water bottle on my bike. The other thing she said was she was having trouble breathing. She was right here lying on the grass. Mm-hmm. But you had no idea how many times she'd actually been -- No. Reporter: Unaware how many times, unaware who did this to her, he watches as the ambulance rushes her away. The hospital less than 4 miles away from that path. So you bring her in here? Her heart rate was very elevated, and her blood pressure was low, so that was very fairly ominous. Reporter: And when you looked at her, it was immediately apparent she'd been stabbed multiple times? Yeah, to her chest, abdomen, arm and leg. Reporter: Doctor's concerned she might not survive. And her mother Stacie has just been told Peyton has been rushed to the hospital. She's also been told it was her best friend Morgan who did this. She calls her husband. I went in the house and called Joe. And I said -- "Peyton's been stabbed. Morgan stabbed Payton. You need to come home." They need to rush Peyton into surgery. So then I really lost it. Reporter: So you got in the car? Got in the car. Reporter: Just minutes later walking in -- So I walked into the trauma room that she was in. And she was pale as a ghost. She was terrified. She was crying. She couldn't breathe. Reporter: But she saw you there? She saw me. And she put her hand out. And I rushed over to her. And I put my arms around her. And I laid next to her. And I hugged her. And I said, "You're gonna be okay. It's gonna be fine." But I could see that she was covered. Her arms and her legs and her abdomen, they were covered in stab wounds. Reporter: They pull her away from her daughter. And she can soon hear the nurses counting. And all I hear is, "There's five on her arm. There's seven on her leg." And I'm thinking, "What? Seven? What?" And one of the nurses says, "All right, I count 19." And then the second nurse said, "I count 19, as well." What? 19? What there's no way. Reporter: There were so many stab wounds, it took two nurses to count them, 19 in all. And her little girl is now being raced down the hall. Then they took her into surgery? Then they take her into surgery. Reporter: Did you say anything to Peyton when they wheeled her away? That I loved her and that she would be okay. Reporter: But there was something else Peyton's mother was thinking at the same time. Morgan didn't do this is what's going through my head. There's no way. There no way that's what's happened. Morgan is 12. Reporter: But that's exactly what investigators believe that Morgan, and only other girl who was invited to that sleep over, Anissa Weier, did this. But they were nowhere to be found. They had run away. And -- and the police hadn't found them yet. And we just knew that Peyton told us Morgan stabbed her. And the police hadn't been able to find the girls. Reporter: And in fact, the police believe those girls were walking. Yep. Reporter: They were going to find a mansion in the woods? They were into the Nicolet forest, because they believed that there was a mansion there that slender man lived in. Reporter: Incredibly police say those girls were now headed to find a mansion where they believed a fictitious internet character truly lived. A character named slender man. Who police say they were hoping to impress. All while their 12-year-old friend Peyton is in the or fighting off death. When we come back -- the doctors who discover, it is worse than anyone thought. We're with the surgeon who saves her. Less than a millimeter. Reporter: Between living and dying? Yes. Reporter: And suddenly authorities find those other two girls. What they reveal about why they did it.
This transcript has been automatically generated and may not be 100% accurate.