assignment for "60 minutes." >> reporter: for more than five years, 1,975 days, american businessman emad shargilic of iran. he spent much of that time in the country's most notorious prison in a dreaded ward run by iran's revolutionary guard. last month, shargi and four other americans were freed in a complicated deal involving $6 billion in restricted iranian oil revenue. the deal drew criticism at the time for granting financial relief to a regime the u.s. government considers the world's largest state sponsor of terrorism. it drew even more scrutiny after hamas, which is financially supported by iran, attacked israel two weeks ago. with more than 200 hostages remaining in gaza, including some americans, shargi's ordeal is a stark illustration of the difficulties and perils involved in bringing american citizens home. >> this story should have never happened. but i didn't waste 5 1/2 years, margaret. i learned a lot about myself, about humanity, about what is important in life. being thrown in a cell, it's the closest you come to death. >> reporter: emad shargi is a dual citizen of the u.s. a