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(CNN NEWSOURCE) He is known by ISIS as the "German"... Abu Talha al-Almani….a notorious ISIS fighter and recruiter; a former German rapper who in intense and disturbing videos called for violent jihad, and proudly held the severed head of an ISIS victim.
Denis Cuspert is his real name. A German national targeted by the United States as a "specially designated global terrorist" who survived a U.S. missile strike in 2015 and is believed to be still alive somewhere in ISIS-controlled Syria.
What has not been disclosed until now is that an FBI employee -with top secret clearance- lied to her bosses, secretly traveled to Syria, and married Cuspert for a short time, becoming the ISIS bride of the very terrorist she was assigned to investigate.
That, now former employee is Daniela Greene. Her face obscured due to concerns for her safety.
Having violated "…the public trust... and endangered our nation's security", according to federal prosecutors, Greene served just two years in prison and is now free.
She wouldn't answer CNN's questions, saying "if I talk to you my family will be in danger."
The information about her case comes from previously sealed court documents.
The records unsealed, only after Greene finished cooperating with authorities, and after prosecutors asked a judge to make them public: "unsealing these documents," they write, "will allow appropriate public access to... this case."
Greene, who was already married, traveled to Syria in the summer of 2014, and not only "spent time in the company of members of... "ISIS" but ended up marrying an infamous ISIS terrorist.
"He is calling upon his followers to commit attacks inside Europe. He says, Europe is a new battleground and he says go and slaughter them, ambush them, shed their blood, take hostages, kill them," said freelance journalist Georg Heil.
Daniela Greene, according to people who knew her, was born in Czechoslovakia, raised in Germany, met and married a U.S. Army soldier.
The U.S. Army brought her husband to South Carolina, where Greene enrolled in Clemson University's history department seeking her master's degree.
"Daniela was a very hardworking, conscientious student," said Clemson University professor Alan Grubb.
Professor Alan Grubb was Greene's thesis adviser.
A few years after graduation, the FBI hired Greene as a translator, assigning her to the Detroit field office.
She was tasked with helping investigate a terrorist-labeled Individual A in court documents – CNN has learned Individual A is the German rapper/turned ISIS fighter, Denis Cuspert.
Greene was able to track the terrorist using three Skype accounts...but it turns out the FBI only knew of only two.
Greene had "sole access to a third Skype account..." and in June 2014, Greene told her supervisor she was making a trip to Germany to visit family.
Instead, she flew through Toronto to Istanbul, traveled south to Gaziantep, Turkey, crossed the Syrian border with the help of the terrorist -- and disappeared.
There, in ISIS-controlled Syria, government prosecutors say Daniela Greene met up with the ISIS terrorist and not only married him but told him "she was employed by the FBI and that the FBI had an open investigation into his activities... "
Professor Alan Grubb says any tale involving terrorism simply could not involve the Daniela Greene he knew.
"So, if I told you that she got wrapped up in a terrorist investigation where she's the target, I would assume that you would find that hard to believe," Drew Griffin, CNN Senior Investigative Correspondent, asked professor Grub. "I would be dumbfounded by that. It would be hard to believe. I don't think there's anything in her background that would suggest to me or any of the people she worked with here proclivities in that direction. So I, yes, I would be surprised."
Shortly after arriving in Syria, Daniela Greene had a change of heart…and within weeks was sending emails back to the United States:
"I was weak"….she wrote in one… "I really made a mess of things this time."
The following day she wrote: "I am gone and I can't come back…. I am in Syria.... I am in a very harsh environment and I don't know how long I will last here, but it doesn't matter, it's all a little too late…"
She went on "I will probably go to prison for a long time if I come back, but that is life... "
On August 6th, 2014 Daniela Greene left Syria, left ISIS and did return to the United States where she was immediately arrested.
Unlike other terrorism-related cases, Daniela Greene's arrest and plea deal would receive no publicity at all from the Department of Justice, the case quietly hidden, court records sealed for months. Even after her case became a matter of public record, still silence.
A look on the FBI and the Department of Justice website shows page after page of press releases about similar terrorist arrests over the years, but this one stayed buried until now.
"This is a very wild tale involving terrorism, the FBI, matters of national security and it's hard to imagine that there would not be public interest in it," CNN investigative reporter Scott Glover said.
He discovered the court documents. "I think it's a fair assessment to say it's embarrassing when an employee with a top secret national security clearance secretly travels to Syria and marries a terrorist who's the subject of the investigation that she's working on."
What is even more stunning about this secretive case is how it ended.
Greene began cooperating with the FBI immediately upon her arrest. She pleaded guilty to making false statements involving international terrorism.
Though the government said she "skirted a line dangerously close to other more serious charges."
The Assistant U.S. Attorney wrote, "the nature and circumstances of this offense warrant serious punishment."
Similar cases have ended in sentences of 8, 10, 15 years in federal prison.
Greene was sentenced to just two.
According to prosecutors, it was because of her cooperation. She's already out, on probation, but free.
As for Denis Cuspert, the German rapper turned ISIS soldier who married the FBI contractor, he remains at large and still a specially designated global terrorist.
The FBI had little to say about this story other than to tell CNN because of Daniela Greene's case the FBI has taken steps to identify and reduce what the bureau calls "vulnerabilities".
As for Greene's seemingly light two-year sentence…a Department of Justice official said that was actually "in-line" with other cases where defendants lied to the FBI about terrorism but then offer "significant cooperation" once under arrest.