Missing New Hampshire Teen's Letter Mystery

Mom gets mysterious letter from missing 15-year-old daughter Abigal Hernandez.
1:48 | 12/07/13

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Transcript for Missing New Hampshire Teen's Letter Mystery
And from new hampshire, troubling new clue in the national search for a missing teenager, 15-year-old abigail hernandez disappearing nearly two months ago. Her mother going before cameras with her emotional pleas, tonight police revealed the mother received a letter believed to be from the daughter, authorities are concerned by what's in it. Here's abc's linzie janis. 15-year-old abigail hernandez mysteriously disappeared on her way home from school two months ago. But tonight, police are revealing a critical lead in the case. A letter they say the new hampshire teen sent to her mother two weeks after she went missing. The reason we are announcing today that we have it, is because law enforcement had to take every possible step to verify its authenticity. And at this juncture, we believe that it was in fact written by abby and was sent to her mother. Reporter: The letter was POSTMARKED OCTOBER 23rd. But didn't reach abby's mother UNTIL NOVEMBER 6th. An fbi investigator working on the case says receiving the letter is unprecedented saying he hasn't seen anything like this in recent investigations. He is hopeful she's alive, but says, she could be in grave danger. Other cases, that we have investigated across the country tell us that one in eight of endangered run aways could be forced into some kind of sexual exploitation, after a situation like this has occurred. Reporter: Although there is a possibility abby left willingly, investigators say it's likely she's being coerced someone. The letter is the only trace of abigail, her cell phone hasn't been used since the day she disappeared. We truly miss you. Reporter: The letter is the only trace of abigail, her cell phone hasn't been used since the day she disappeared. Linzie janis back on the case again.

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