On Monday May 22 Four Corners will present the first episode in a two-part special investigation into the Lindt Cafe siege.

Sarah Ferguson talks exclusively with the families of Tori Johnson and Katrina Dawson about their experience on the day and their devastation, anger and frustrations in the aftermath of the siege.

Surviving hostages recount their terrifying ordeal as they waited, hour after hour, for the police to arrive.

The program examines how authorities over several years failed to comprehend the risk posed by hostage taker Man Haron Monis.

Part two of the investigation will take you inside the Lindt Cafe and the police operation on the day, and bring you a forensic examination of how the disaster unfolded.

This special investigation exposes what went wrong and questions whether Australia is prepared for another terror attack.

The NSW Coroner will deliver his findings on the siege on Wednesday May 24.

Part One of The Lindt Cafe Siege, reported and presented by Sarah Ferguson, goes to air on Monday 22nd May at 8.30pm on ABC & ABC iview. It is replayed on Tuesday 23rd May at 10.00am and Wednesday 24th at 11pm. It can also be seen on the ABC NEWS channel on Saturday at 8.00pm AEST, ABC iview and at abc.net.au/4corners.