[1] Police investigations revealed that, on the day of their disappearance, several witnesses had seen the three children on and near Glenelg Beach in the company of a tall man with fairish to light-brown hair and a thin face with a sun-tanned complexion and medium build, aged in his mid-thirties.

The case received worldwide attention and is credited with causing a change in Australian lifestyles, since parents began to believe that their children could no longer be presumed to be safe when unsupervised in public.

On 25 January 1966, in the midst of a summer heatwave, Jim dropped the children off at Glenelg Beach before heading off on a three-day sales trip to Snowtown.

[2][11] Police quickly organised a search of Glenelg Beach and adjacent areas, based on the assumption that the Beaumont children were nearby and had simply lost track of time.

The search then expanded to the sand-hills, ocean and nearby buildings, with the airport, rail lines and interstate roads being monitored as well, based on a fear of accident or kidnap.

[16] Police investigating the case found several witnesses who had seen the Beaumont children in Colley Reserve, near Glenelg Beach, in the company of a tall man with fair to light brown hair and a thin face, and in his mid-thirties.

[20] About two-and-a-half hours later another witness, Miss Daphne Gregory, sighted the children with the man, who she observed carrying an airline bag similar to one owned by Jane.

[23] A chance remark at home, which seemed insignificant at the time, supports this theory: Arnna had told her mother that Jane had "got a boyfriend down the beach".

[14]: 37 Several months later, a woman reported that on the night of the disappearance, a man, accompanied by two girls and a boy, entered a neighbouring house that she had believed empty.

Some time later a third letter arrived, also purported to be from Jane, stating that the man had realised a disguised detective was present and that he decided to keep the children because the Beaumonts had betrayed his trust.

[25][26][38] In November 2013, excavation was initiated in the back of a North Plympton factory that had previously belonged to Harry Phipps, a possible suspect in the Beaumont case.

[43] He related an alleged conversation in which von Einem boasted of having taken three children from a beach several years earlier, and said he had taken them home to conduct "experiments".

[45] According to Adelaide police detective Bob O'Brien, Mr B had given important information during the investigation into the Kelvin murder and was regarded as a generally reliable source.

[42] Investigations into both the Beaumont disappearance and the Adelaide Oval abductions remain officially open and, in 1989, von Einem was identified as a suspect in a confidential police report.

[45] In August 2007, it was reported that police were examining archival footage from the original Beaumont search, shot by Channel Seven, that shows a young man resembling von Einem among onlookers.

[52] A search for a connection to the Beaumont children was unsuccessful as no employment records existed that could shed light on Brown's movements at the time.

James O'Neill (born 1947), who was sentenced to life imprisonment for the 1975 murder of a nine-year-old boy in Tasmania, is reported to have previously told several acquaintances that he was responsible for the Beaumont disappearance.

In 2006, O'Neill lost an injunction in the High Court of Australia to stop the broadcast of an ABC documentary, The Fishermen, which attempted to link him to the case.

[56] Derek Percy (1948–2013), a convicted child murderer and Victoria's then-longest-serving prisoner, was suggested in a 2007 article in Melbourne's The Age newspaper as a suspect in the Beaumont case.

His insanity plea in the 1969 murder of Yvonne Tuohy was at least partly based on his suffering a psychological condition that could prevent him remembering details of his actions.

[60] Percy was imprisoned from 1969 until his death in 2013, which means that he could not have been the suspect in the Adelaide Oval abductions, whom many investigators believe to be connected to the Beaumont case.

Alan Maxwell McIntyre (died 2017[61])—who had himself been investigated by police and cleared of involvement in the Beaumont case—gave a secondhand account to the Adelaide Advertiser that a man he had known in 1966, who by 2015 was being sought in Southeast Asia in connection with child abuse incidents there, had come to his home with the children's bodies in the boot of his car.

[62] The man in question was later identified as businessman Alan Anthony Munro (aged 75 in 2017), a former scoutmaster who had pleaded guilty to ten child sex offences dating back to 1962.

[11] In June 2017, Adelaide police detectives were given a copy of a child's diary, written in 1966, which allegedly placed Munro in the vicinity of Glenelg Beach at the time of the Beaumont disappearance.

[64] Harry Phipps (died 2004), a local factory owner and then-member of Adelaide's social elite, came to attention as a possible suspect after the publication of the book The Satin Man: Uncovering the Mystery of the Missing Beaumont Children in 2013.

[72][73] The kidnapping is also viewed by many social commentators as a significant event in the evolution of Australian society, with a large number of people changing the way they supervised their children daily.

[3][4] At the time, it was never publicly suggested that the children should not have been allowed to travel unsupervised, or that their parents were in any way negligent, simply because contemporary Australian society took it for granted that this was safe and acceptable.

[5] However, this case, alongside similar child-related crimes such as the 1960 Graeme Thorne kidnapping and the 1965 Wanda Beach murders "marked an end of innocence in [post-war] Australian life".

[6][7] The regular and widespread attention given to this case, its significance in Australian criminal history and the fact that the mystery of their disappearance has never been explained have led to the story being continually revisited by the media.

The fact that the case has never been explained has led to the story being continually revisited by the media, and by newer online sites, more than fifty years after the children's disappearance.