On 23 or 24 February 1968, Jim Beaumont received a letter, purportedly from his daughter Jane. He phoned the officer in charge of the case, detective-sergeant Stan Swaine, who immediately visited.
The letter had been posted in Dandenong, Victoria on 21 February. The handwriting was not very similar to Jane's, but both Mrs Beaumont and Stan Swaine believed she'd written it. The letter said that the Beaumont children would be returned to their parents. Mr Beaumont was to be in front of the Dandenong post office at 8:50am on Monday 26 February, wearing a dark coat and white trousers. If the police were informed the deal would be off. Arnna's name was continually misspelt as "Arna" in the letter.
At 5am on Sunday the Beaumonts, with Swaine and another man named Bill Cotton, left for Dandenong. The Beaumonts checked into the Commodore Motel under the name of Ellis. The operation was meant to be conducted in the greatest secrecy and the Victoria Police were not informed. Dandenong is not far from Melbourne.
Somebody tipped off the Adelaide newspaper the News about the story. On the Sunday afternoon the story was leaked. Two cars of reporters followed the Beaumonts to Dandenong. Like the police, they were in position by 7am the next day to see what would happen.
It transpired that the story would have been revealed even without the breach of secrecy. The publican of the pub where Swaine had booked a room was aware that several safes had recently been robbed in the area. As Swaine was a stranger, the publican phoned a Dandenong police sergeant and asked him to investigate Swaine. The Dandenong sergeant did so and discovered that Swaine was a detective-sergeant from Adelaide. Thinking this peculiar, the police sergeant rang the Melbourne Herald newspaper. Douglas Steele of the Herald recognised the name of Swaine as the detective who'd been on the Beaumont case. Steele immediately despatched two reporters, who saw the entire set up.
Swaine moved in and around the area of the post office, keeping it under surveillance while appearing to be wandering aimlessly. Before 9am, Jim Beaumont arrived at the post office and waited in front of it, as per instructions. At 9am a phone call was answered by Alice Parker, a post office worker. A voice with a male Australian accent told her to take a message to the man outside. The message which Mrs Parker delivered to Mr Beaumont was that they wouldn't be long. Mr Beaumont thanked her, and on returning inside the post office Mrs Parker commented that the man outside looked like Jim Beaumont.
A short time later a messenger boy from the telegram room emerged, giving Mr Beaumont a similar message. Mr Beaumont crossed the road as a result of this or another message. One message was received saying that Grant was sick and could not come until after lunch. Mr Beaumont finally quit at about 3pm. He appeared again on the 27th, and across the road on the 28th. The children were not returned to him.
On the afternoon of the first day, the journalists from the News encountered Swaine and the Beaumonts in a local pub. It was the first that Swaine or the Beaumonts knew that the details of the operation had been leaked.
Three more letters were sent to the Beaumont's home, in two envelopes. One envelope was posted at Dandenong on 29 February, the other may have been posted on the same day but carried no marking by which this could be determined. Two of these letters were written in the same hand as before, by "Jane". The other was in disguised handwriting and signed "The Man". The letters said that the Beaumont children were not being returned because Mr and Mrs Beaumont had informed the police about receiving the first letter.
In 1981 the letters were re-examined but yielded no new evidence. In May 1992, new fingerprint techniques applied by the technical services section of the South Australian police enabled the author of the letters to be identified. He was a 41 year old man who had written the letters, when aged 17, as "a joke." Following examination of his handwriting and questioning by detective senior sergeant Trevor Couch, the man admitted writing the letters. The officer in charge of the Major Crime Task Force, detective superintendent Jim Litster, announced: 75
"We are able to confirm the letters were in fact written by the male person, they were a hoax, and were in no way connected with the disappearance of the three children. I understand the person involved is extremely remorseful and it would seem that an act he has carried out as an immature young person has come back to haunt him. Owing to the limitation of time statutes, no charges will be preferred."