Transcript for Boyfriend, girlfriend travel to Europe during murder investigation
Reporter: It's been six months since the heinous double-murder of Derek and Nancy haysom rocked the rural community of Bedford county, Virginia. There have been no arrests, but the haysoms' youngest daughter Elizabeth haysom and her German boyfriend Jens soering are under suspicion. With limited evidence, police are left to wait for Jens to voluntarily give his fingerprints and blood. Reporter: Jens says he'll go think about it. Calls a few days later and says he will, in fact, submit? He said, "I've been busy with a paper, I'll do it next Wednesday. I can't do it this week." Reporter: But before the set appointment with Jens, a shocking setback. Dr. Howard haysom called us. And I will never forget that phone call. He was upset. And he said, "You've-- you know, you've let 'em get away." And so they vanished. Reporter: Into thin air? Into thin air. I said, "Well, apparently they're both guilty of something'. Otherwise, why would they leave?" Reporter: Unbeknownst to Virginia investigators, the couple is 4,000 miles away in Europe on their way in a jet-setting globetrotting journey across the world, keeping a journal of their exploits, along with maps and receipts for their international ports of call. This is when they were traveling. Reporter: Here's something from stuttgart. Something from Luxembourg. Shilling. Reporter: Oh, this is Bangkok. This is a map of Bangkok. They had quite the journey on the run, didn't they? They sure did. Let's picture these two young lovers going on this romantic, tense, crazy adventure to England. Life on the lam in London. Yeah, under assumed names, passing bag checks, but then it all came crashing down on them. Reporter: Jens and Elizabeth's six-month life on the lam ended in this London marks & Spencer department store. On the 30th of April, 1986, a young couple was seen by the store detective in marks and Spencer, just across the road there, acting suspiciously. Reporter: Terry Wright and Kenneth beever were detectives with the London police department. They were separated inside the store and they both were seen to go to the counter and get refunds off previous purchases. Reporter: A store detective alerts an off-duty officer who stops the young couple. They said their names were Christopher plat Noe, and Lucy Noe. His hair was tinted very slightly reddish, wasn't it? Yes. She had dark hair, fairly short. I wanted to know where they were staying in London, and I wanted to know where their passports where. Reporter: Jens then makes a decision, a fatal mistake according to detectives that will alter the course of his and Elizabeth's lives forever. He decided to tell us that he was staying at a place called at home, which is a small basement rental apartment in gloucester place in the center of London. Reporter: As fate would have it, the London flat was just off baker street, the fictional home of Sherlock Holmes. This is exactly the same as the place that Jens brought us to. Down some basement steps, the doorway on the right hand side. Jens had a key on him. He opened the door, and took us into what was a very, very small room. I noticed on the bed, there were some wigs, false mustaches, false beards, and I simply realized that Jens, during the whole time he was talking to us, was wearing a false mustache. I can remember Terry saying to Jens, "Okay, take it off." Jens pulled off the mustache for us. Reporter: But among the weary travelers' masks and veneers, detectives are about to uncover a bona fide bombshell. There was one suitcase in particular that was very large and it was full of correspondence. Once he started going through the letters and the diaries, it opened up a can of worms. Reporter: Those steamy letters they have written to each other and a shared travel diary, pages of entries would reveal clues to a macabre secret. That correspondence all now locked up in a Bedford county evidence room. Reporter: These are all the letters and things that were found in their room in London, right? These are letters. And I believe this is going to be Elizabeth's diary. Reporter: In it, Elizabeth writes passages incriminating herself and Jens. Jens wipes fingerprints from room. Passport photos done. Parks at national airport satellite parking. Wipes car. Wipes car. I'm thinking, why are they worried about fingerprints? It seemed to me like they were trying to hide something. Reporter: She goes on to write, "We were told the case is about to be solved. Perhaps fingerprints on coffee mug used by Jens in Bedford interview gave him away." Now clearly again, they were worried about fingerprints for some reason, and I wanted to know what that interview was. I went and got him a cup of coffee the day we interviewed him. I believe a styrofoam cup is all they had. So no fingerprints were gotten off of it. Reporter: As detectives read on, they learn Elizabeth has been harboring a deep hatred for her parents. There was also letters that were talking about things like doing voodoo on her parents and I wish they would lie down and die. The chrtmas letters were so biting and so full of hatred that Elizabeth wrote Jens. Reporter: About her parents? About her parents and how much she despised them. And she talked about, should we get rid of them now or should we wait until he graduate, and then do that? Reporter: And the young couple's clumsy trail of bread crumbs is about to lead right back to Bedford county, Virginia, because in yet another of the letters written by Jens, he mentions the names of two homicide detectives in the U.S. One of them referred to, was actually address to dear officers Reid and Gardner. I found that particularly interesting because it actually referred to death of her parents. Reporter: Elementary, as Sherlock Holmes would say. I kept telling everybody that I thought, I'd already decided I thought they'd done a murder. And I got the phone call. He said, "This is detective constable Terry Wright Callin' from Richmond, England." He said-- "Do you know Elizabeth haysom and Jens soering?" Reporter: Okay. Now you have to be -- And I'm going, yeah. Yeah, I do. I said "Can you tell me, are her parents dead?" He said, "Yeah, they're dead." He said, "Were they murdered?" And I said, "Yes." I said, "I think you need to come over." We have the murderers incarcerated.
This transcript has been automatically generated and may not be 100% accurate.