As one believer put it: "The cats are out there - and they're breeding."
Farmers, wildlife rangers and conspiracy theorists take photos of scratchings on trees and collect scat samples, hairs and "panther paws" moulds.
There have been more than 460 sightings in the Hawkesbury since 2001, making it the big cat capital of Australia, and to help in our quest we met with five local "experts" - a politician, an author, a big cat hunter, a witness and a political activist.
Just like former premier Nathan Rees, Hawkesbury Council mayor Bart Bassett is a believer.
"There have been too many sightings by too many reputable people for it not to be true," Mr Bassett said.
"We're talking about a dentist, a retired magistrate and actual Department of Primary Industries staff."
Our search takes us into the Grose Valley, where there have been more than 64 sightings of the black cat.
Big cat hunter Craig Rye from the Central Coast sets up game cameras in the Hawkesbury hoping to capture the million-dollar shot of the cat.
"It was about three years ago when I started to take an interest in the cat," Mr Rye said. "Ever since, I've been tracking its movements and setting up cameras. Nobody's seen it but it's there."
Mr Rye sets up a camera and a T-bone trap on a tree close to the tiny cottage where we have set up camp.
Big Cat database founder and political lobbyist Chris Coffey, who lives up the road, said dead wallabies had been found near his cottage.
"If you're going to see it, that's the perfect spot," Mr Coffey said.
Our search for the panther doesn't go to plan. The T-bone trap didn't work and the can of Whiskas attracted possums.
Instead of relaxing in front of the fire in our timber cottage, we grab our torches and head into the bush.
A clear night sky and bright moon provide some light but, once we're deep in the bush, it's like walking blind.
With our socks pulled up high to keep leeches away, we follow a wallaby track through the Grose Valley.
After spending the day interviewing big cat believers, my senses are heightened.
My eyes are fixed on moving bushes and my hearing is honed in to every rustle of every leaf. After a short walk, the realisation hits - it's a waste of time.
If the big cat is as lethal and predatory as we are told, we wouldn't know what had hit us if it decided to pounce.
We trudge back to the cabin, keeping watch throughout the night for any movement near our elaborate T-bone trap.
As hope faded in our search for the Lithgow Panther, we receive a tip-off that a scat sample taken from Pindar Cave in the Brisbane Water National Park had tested positive for cat. The sample, tested by the DPI, contained wallaby fur and bones.
But the final word should go to Mike Williams and partner Rebecca Lang who spent 10 years interviewing more than 750 witnesses from across Australia for their book Australian Big Cats: An Unnatural History Of Panthers.
"There has been so many discrepancies with government testing of scat and fur samples. There is a big cat out there," said Mr Williams.