On September 13, 1842, one Henry Dunkley was hacked to death with an axe by his servant in a cottage in Gunning, north of Canberra.

The man who beheaded his master then took to bed with the newly bereaved wife and the two enjoyed sex and alcohol until officers of the law disturbed their bliss.

The widow, Lucretia, and her lover, Martin Beech, were eventually hanged. The court decided they were both equally steeped in blood.

Every detail is macabre - the two were apparently buried standing up so that they would never rest in peace. Their skulls were removed and remain locked from public view in the vaults of the Australian Museum in Sydney.

It seems the murderous widow - the perpetrator of mariticide - was pregnant when she was hanged. Was the father of the unborn child the murderer or his victim - or someone else?

Dunkley's grave is in what was to become the Gunning sewage plant. On it is the inscription, "cruelly and barbarously murdered by his wife and manservant".

It is a horror story fit for a movie - and that's what it has now become.

Canberra film-maker Sebastian Chan and producer Justin Bush have made a short film, which is to be premiered at the Historical Society of Gunning on Saturday night.

The Tragedy of Henry Dunkley is of high professional standards, with a lot of time-lapse and drone shooting.

It's a drama-documentary presented by Tim the Yowie Man, the Canberra celebrity who often appears in these pages. "It's showcasing part of our region's history to a new generation and that's important," he said.

Some scenes are dramatised with actors, with recreations of the grisly events tastefully shot in silhouette and similar filmic techniques to avoid overly gory depiction. It won't frighten the kids but will engross the adults.

And there may or may not be a guest appearance by a ghost.

Tim visits the courthouse in Berrima where the two culprits were tried. He takes along a team of ghost-busters, including Graham Lewis who has modified an X-Box camera to detect images invisible to the naked eye.

Mr Lewis told The Canberra Times that his ghost-detector was a camera that was originally designed to detect movements by people playing on-screen games. He realised that, with modification and some new computer code, it could be made to detect ghosts. He said it had worked in haunted places elsewhere.

So did he detect the ghosts of the murderous couple in the Berrima courthouse? You'll have to watch the film to find out.

The story of the love-triangle and the murder was first revealed by Keith Brown from the Gunning and District Historical Society.

The former diplomat and deputy secretary to two governors-general wrote The Day that Dunkley Died: Murder and Retribution in Colonial Gunning, which outlines the grisly events of the fatal night - the beheading of the victim and the disposal of the body by the two lovers.

While the slab hut where Dunkley met his end is yet to be discovered, Mr Brown believed that he had identified the site.

When he was interviewed two years ago, he said, "While he was definitely hacked to death by an axe, my investigations show that his body was found where Beech had buried it, just near this creek" pointing at the time towards Meadow Creek, which meandered through Wagahrallah, a sheep and cattle run.

Mr Brown tried and failed to find traces of the slab-hut habitation with a metal detector on the assumption that coins or cooking pots might be buried.

The two were hanged on October 16, 1843 at Berrima Gaol, according to Mr Brown. "The bodies of Beech and his accomplice are buried inside the walls of the prison apparently standing up so they could never rest in peace."

The Morning Chronicle of October 21, 1843 reported "both prisoners exhibited the like apathy upon the scaffold, and died as they had lived, hardened and unrepentant".

The two murderous lovers were buried in the jail though the exact location isn't known. Mr Brown said that two crosses on a sandstone block might offer a very grisly clue.

"In the process of being hanged Lucretia aborted a foetus and it is likely those two crosses indicate the burial spot of Lucretia and her unborn child," explained the sleuth.

Brutality haunted them even after death in that their skulls were removed to be studied. There was a pseudo-science at the time called phrenology - the belief that criminals had different shaped brains and heads.

The macabre stranger-than-fiction truth has now become a short film, which is well worth watching.

The Tragedy of Henry Dunkley will be shown at the Gunning Fire Control Centre (next to Pye Cottage) on Saturday at 6pm, then published on the web. Email gunninghistory@gmail.com for tickets.