The prisoner in question was once on the list of America’s most-wanted terrorists: Aafia Siddiqui, a Pakistani-born neuroscientist who studied at MIT and Brandeis. Soon after 9/11 she was named as part of a close-knit group around that attack’s mastermind, Khalid Sheikh Mohammed. She had married one of his top deputies. When she finally was caught in Afghanistan in 2008 she allegedly carried plans to make dirty bombs and weaponize the Ebola virus. She also managed to grab a gun while she was being questioned and tried to kill the American soldiers at the interrogation session.

Siddiqui comes from an influential Pakistani family, and her supporters say she was railroaded or framed. But ISIS and, before it, Al Qaeda, often have mentioned made her release a condition in hostage negotiations.

The Muellers decided to appeal to Obama as the clock ticked down on a 30-day deadline ISIS imposed to free Siddiqui last summer. “Kayla’s parents would have done anything they could for their daughter, as any parents would, and they thought it was worth exploring any and all options,” a family representative told The Daily Beast.