How an Aussie mother helped solve famous UK author's mysterious murder.

As she spoke to police who were once again scouring the home next-door in search of its missing owner, Nicky McGrath suddenly recalled something. A grim, offhand joke by the former resident of the sprawling Hertfordshire property.

About to head back inside her mother’s home, McGrath stopped, and then asked the question that would help put an end to a mystery that had captivated the UK and baffled investigators for more than three months – the disappearance of famous British author Helen Bailey.

That question?

“It might sound stupid, but have you dredged the well?”

Helen Bailey's sprawling Hertfordshire, estate, Hartwell Lodge. via Google Earth.

On April 11, 51-year-old children's author Helen Bailey went for a walk with her little dachshund Boris and never returned, reports The Daily Mail. An extensive search of the grand, multi-million-dollar property she shared with her partner, Ian Stewart, and his two sons returned no clues.

With her money withdrawn from her account, police began to come to the conclusion that the famous Electra Brown and Daisy Davenport writer had actually wanted to disappear, potentially forever, but friends vehemently denied the claim.

With no clues, no leads and no closer to an answer, police returned to the Hertfordshire home again last week. The five-day search could have proved as fruitless as the first, were it not for Nicky McGrath.

The Perth-based mother of three was visiting her mother who lived next-door to Bailey, when she approached police to complain about the noise of their generators late last week. It was then that recalled the former owner of the property joking about the well being "the perfect place to dump a body".

“The senior officer came to see us the next morning and we told him what we knew. Then my mum phoned the former owner of the house so the detective could speak directly to him," McGrath later told reporters, according to The Daily Mail.

“It turned out the police had only been draining the overflow tank in the old well in the garden, thinking that was all there was. The former owner told them the actual cesspit was in the large garage at the back of the house.

“The body was found a little while later."

Bailey had been widowed five years ago, after tragically watching her husband drown while on holiday in Barbados. The grief was overwhelming, but seven months later, love once again returned to her life in the form of a grey-haired, IT specialist named Ian Stewart.

Himself a widower, 55-year-old Stewart seemed shattered by Bailey's sudden disappearance and publicly pleaded for her safe return.

“Helen, wherever you might be I hope you hear this message and listen carefully. We miss you and Boris so much. We are shattered in so many ways. Whatever has happened, wherever you are I will come and get you and Boris and give you whatever you need.”

He claimed to have found a note from Bailey saying she wished to spend some time alone at her holiday house in Kent.

But it was Stewart who was last week charged with her murder. He also faces charges of perverting the course of justice and preventing a lawful burial.

The remains of Boris, Bailey's dog, were also found on the property.

It remains unclear how Bailey died. The investigation continues.