Four prisoners - Iranian-Americans Siamak Namazi, Emad Sharqi, Morad Tahbaz, as well as another prisoner whose name has not been disclosed. The next step in a deal could be the transfer of $6 billion of Iranian funds frozen in South Korea to a special account in Qatar. "I think this is the beginning of the end of their nightmare and that of their families," says US Foreign Minister Antony Blinken. The four were escorted to a hotel where they will remain under police surveillance, according to the lawyer of one of the prisoners.