Was a young girl adopted from Russia capable of murder?

For years, he tried to find out what became of Caralee, and last summer they reunited and he learned her surprising story.

Crystal and Jesse — "48 Hours" agreed not to use their last name — are both 30 and have tried for years to have a child of their own.

Troy Roberts: You understood, though, that adopting an older child carries certain risks.

Troy Roberts: You understood that.

Didn't cry at all, but just very angry.

Crystal:  Caralee … had just gotten a new bike and we were learning how to ride it.

Troy Roberts: Are you afraid of Caralee?

She spent almost four months under constant care before Crystal and Jesse say their insurance started running out, and they were forced to bring Caralee back into their home again.

Troy Roberts: That's why you have to get help.

Troy Roberts: You love her, but yet you're frightened of her.

They say Caralee tried strangling the family dog, Aurora.

Troy Roberts: "Caralee is emotionally nice.

Only after the adoption was official, Crystal and Jesse say, did the Frank Foundation provide them with more documents that revealed troubling things about Caralee's past.

Crystal and Jesse believe the mistreatment had a lasting effect on Caralee.

Troy Roberts: You would not have adopted her.

Troy Roberts: You didn't hide any information.

Crystal: So, Caralee most likely will just move on.

Troy Roberts: They say that she tried to kill her little brother...

Troy Roberts: They say that she tried to kill the family dog.

After treating Caralee, he wrote, "Caralee's behavior … was impeccable." He said the staff perceived that Crystal and Jesse were "too often cool and distant" towards their daughter, and that "Caralee at times, appeared to be frightened by her interactions with them.".

Crystal: Caralee is a very different person when you really get to know her.

… She's already tried it once.  It's a very strong possibility she'll try it again with success.

Troy Roberts: So, Caralee understands that she is here to be treated by Russian specialists.

Then just a few minutes before she'll enter the hospital, Caralee tells me something she's never told me before.

Troy Roberts: You didn't try to kill Joshua.

Caralee: I just tried to just pick him up, that's all, because he was too heavy.

But Crystal and Jesse have made a final decision.  They're not bringing Caralee back.

Sabrina Caldwell: It's been so long.

Sabrina Caldwell: Making babies.

Sabrina Caldwell: Yeah.

And what she thought went wrong with Jesse and Crystal.

Sabrina Caldwell: I did!

Troy Roberts: You liked him.

Sabrina Caldwell: I did.

Troy Roberts: Did that create any jealousy?

Sabrina Caldwell: … it didn't create jealousy … I felt more down.

Troy Roberts: You didn't have — an emotional connection with Crystal and Jesse.

Sabrina Caldwell: Because Joshua was so centered, I think we lost it.

Sabrina Caldwell: I was very suicidal … There were days … I'd try to attempt multiple times and I just couldn't do it.

… when I started creating a story … I told Crystal … "You know, I'm seeing and hearing things.

Troy Roberts: So, were you hallucinating at that time?

Sabrina Caldwell: No … no hearing, no seeing things?

Sabrina Caldwell: Crystal was gardening, and Joshua was screaming on top of the deck.

And Crystal said, "I need you to go get Joshua." … Tryin' to pick up a child that's really almost as big as you is kinda hard … So, I'm tryin' to walk down the steps … just able to hold him so he doesn't fall … Crystal looked.

Sabrina Caldwell: "Put him down.".

Sabrina Caldwell: I eventually put him down and she was like, "You tried to kill him, didn't you?" And I said, "No.

Sabrina repeated that story that she tried to kill Joshua to everyone — including me.

TROY ROBERTS to CARALEE [1999]: What happened that day out on the deck?

Sabrina Caldwell: I went to psychiatrist after psychiatrist.

And I remember Crystal saying, "Just remember, you wanted to kill Joshua." I said, "OK.

Troy Roberts: Dr.

Sabrina Caldwell: Hmm.

Troy Roberts: You were also accused of tryin' to kill the family dog.

Sabrina Caldwell: I don't know where that came from because I loved that dog (laughs).

Troy Roberts: … how did you learn that you were going back to Russia.

Sabrina Caldwell: Crystal said (sighs) they were running out of options.

TROY ROBERTS [1999 in the Russian hospital]: So how is it going here?

TROY ROBERTS: Not good.

Troy Roberts: How did that make you feel, when you were sitting there in — in the hospital in Moscow, waiting for them to return to pick you up, and they didn't.

Sabrina Caldwell: I knew they weren't coming.

Troy Roberts: I felt so guilty.

Sabrina Caldwell: I wanted you to take me (laughs).

Sabrina Caldwell:  I felt like I was in jail … but then I think of it — I put myself there … You know, all those lying and doing what they want me to do.

Sabrina Caldwell: Nina showed up and she brought me clothes.

Sabrina Caldwell: I have parents … they're the parents that took me in, that took their time to learn who I am and make me a better person.

Sabrina Caldwell: Loved it ….

Sabrina Caldwell: I did.

Sabrina Caldwell: I fell in love him when I saw him interact with kids.

Phil Caldwell: She's just very real and very genuine.

Sabrina Caldwell: … fun kids.

Sabrina Caldwell: I am.

Sabrina Caldwell: I am.

But Sabrina, like me, has always wondered what happened to Crystal and Jesse, and she says, that after two decades, she was ready to find out.

After she became a mother, Sabrina says, she wanted Crystal and Jesse to know she had a family of her own, and she wanted to share her side of the story.

Sabrina Caldwell: I … sent her a message – stating to her that I hope she's well, and … "I just wanna make this really clear for you, I've never wanted to hurt Joshua and I never heard or saw things in my life.

Sabrina Caldwell: … she said she prayed that I would have a better family.

Troy Roberts: Did you love Crystal and Jesse.

Sabrina Caldwell: I did.

Sabrina Caldwell: Putting myself in their shoes, I would have probably done almost the same thing!

Sabrina Caldwell: I would never take a child back. .

Sabrina Caldwell: I learned … to forgive my past.

Sabrina Caldwell: I have an amazing husband.

Sabrina says Crystal and Jesse have three biological daughters of their own, along with Joshua.

However, Jesse said that he and Crystal were glad Sabrina's life had turned out so well, and that Joshua was now a father, too.

In the end, it appears that Crystal and Jesse, like Sabrina, eventually found families and happiness.

Troy Roberts: I cried as I was leaving … then I started saying to myself, you know … "Maybe one day, I can rescue an — an older child… ".

Troy Roberts: And then, I had a story in Johannesburg, South Africa … and I went to an orphanage there to make a donation.

… I said, you know what, I'm close to 40 now.

Troy Roberts: And I looked at his photo and the resemblance was uncanny … This looks like my kid

Troy Roberts: … they were homeless and living in an abandoned building

He didn't know how to swim, so we took a boat to this small little beach island that was reserved for the military personnel

Troy Roberts: Khadra … never signed her name before

She didn't know how to sign her name

Jonah Roberts: I was just, "there's a man here who's, you know, taking care of me, who's feeding me" … He also did get me a tutor so I was getting education … at that age you don't really think anything about it, you're just, "this could be my long-lost dad."

Jonah Roberts: Then my dad tells me, "Oh, we're in New York City, this is your new home." … And I remember seeing my first home, my first real home … and he's like, "this is your room." … It was my own bed; I didn't have to share it with anyone

Troy Roberts: … we did everything together, so much together … I really enjoyed watching him learn new things and introducing him to a whole new world

Jonah Roberts: There was never father and adopted son … It was always, you know, father and son

Jonah Roberts: Every Thanksgiving, we have this thing where before we start eating, after I've made the full meal …  because he doesn't know how to cook — we would always start off by saying, like, what we're grateful for this year

Troy Roberts: … it seems everyone's story has a happy ending, and that's pretty cool, you know