Christiane Amanpour on ISIS

Renu Begum, eldest sister of Shamima Begum, 15, holds her sister's photo as she is interviewed at New Scotland Yard, as the relatives of 3 missing schoolgirls believed to have fled to Syria.

Christiane Amanpour, chief international correspondent for CNN, discusses developments with ISIS, including the identification of "Jihadi John" as Londoner Mohammed Emwazi. Plus: the latest on Iranian nuclear talks.