In a baking hot detention camp in Syria, a large group of Australian women and children are being held indefinitely. They're the remnants of the Australian contingent who lived under Islamic State. The Australian Government has branded them a "significant security threat" and made it clear it does not want them back. There are 20 women and more than 40 children stuck in the al-Hawl camp. Who they are and how they got there has until now, remained secret. Now for the first time, their stories are being told. In this exclusive Four Corners investigation, the former brides of Islamic State reveal the extraordinary details of their lives in the IS caliphate.