A murder mystery that started in Allenstown 37 years ago has taken investigators from New Hampshire to California, and the final piece of the puzzle may be in Mississippi.This investigation started in 1985 when the bodies of a woman and a girl were discovered in a barrel near Bear Brook State Park. In 2000, two more bodies were discovered in a second barrel.DNA and genealogical research have identified three of the victims, but investigators still don't know the name of the last girl, the middle child.DNA samples have played a key role in connecting the genealogical dots of the Allenstown murder case, and investigators expect that's how they'll learn the identity of the last unknown victim. But many people are hesitant to hand over their most personal biological information."Initially, I would start with, 'I'm working on a cold case, and I'm hoping you can help me out,'" said Deputy Peter Headley, of the San Bernardino Sheriff's Department in California. "That usually would pique their curiosity. When, where, you know. And then I would go into details."The investigation has been at the forefront of a new kind of detective work: genetic genealogy. It combines the information from DNA samples and ancestry databases.New Hampshire State Police said websites such as Family Tree DNA and GEDmatch offer the chance to make connections while protecting the privacy of the people submitting genetic information.For the Allenstown case, officials said a single investigator is the only person with access to DNA profiles. It takes her about five minutes to compare someone's information to the victim."And then she can close out the file, and if the people want to remain closed out, no one else would be able to access it," said Sgt. Matthew Koehler, of the New Hampshire State Police. "I have found that most of the people are willing to cooperate. Most of the people want us to be successful. Some choose not to. They have concerns, and we respect that. We leave it alone, and we move on to the next potential match."In the Allenstown case, the genealogical research has led detectives to Pearl River County, Mississippi, where they have found ancestors of the unknown girl's mother."We believe the great-grandfather, if you will, the patriarch of the family, is a gentleman named Thomas Mitchell, commonly referred to as Thomas Deadhorse Mitchell," Koehler said.Since releasing that information, investigators said they have discovered several potential leads.There is a fee to upload DNA, but investigators said there is also financial help for anyone who can't afford the charge. Much of that is covered by contributions from other donors.They said the new approach is offering hope to families in other cases who thought there was nowhere left to look."Please join all the ancestry sites," Headley said. "Family Tree DNA and GEDMatch especially. If you've got missing loved ones, you've got a shot at some closure now. You really do."