Based on real events in Melbourne, Victoria, between 1995 and 2004, Underbelly tells the story of the gangland war, known as the Melbourne gangland killings, between rival factions of Melbourne's criminal underworld. This major primetime production based on true events features an all-star cast from Australia. Season 4: set during the roaring 20's in Sydney when organised crime in Australia began. It is the story of the bloody battle between the era's most feared vice queens, Tilly Devine and her rival Kate Leigh.