Peter Kassig's mother implores ISIS to "show mercy"

The family of ISIS hostage and U.S. aid worker Peter Kassig released a YouTube video Saturday asking his captors to show mercy and free him.

Referring to him as Abdul-Rahman - a first name his family says he took, having converted to Islam while being held hostage - father Ed Kassig said: "We implore his captors to show mercy and use their power to let our son go."

The clock is ticking with Kassig's life in the balance after he appeared in the beheading video of British hostage Alan Henning last week.

CNN's Joe Johns is OutFront with more on his family's appeal for his safe return.