Walter Scott arrived in Australia, aboard the S.S. Ayrshire on 23 October 1910 from Liverpool, England. He may have been a sailor on the ship as at that stage young boys were still taken on by the merchant navy. He worked for a short time for a Mr. Angus, and Sherlock, South Australia, and then for a Mr. E. Jenkins (for about two weeks), and then on another farm, that of Mr. E. Jenkins for one week. Walter Scott wrote to his mother on 10 December 1910, and then disappeared. His mother then instituted an inquiry through a J. S. Meikle, of stone Leigh, Manley Road, Waterloo, Liverpool England.
A notice to this effect was published in the South Australian Police Gazette of 19 February 1913. 
He married Mabel Smith in 1915 in Stockton, New South Wales, Australia. His son, Walter James Caldwell, was born in Stockton on 3 January 1917, and died shortly after his birth.
Walter enlisted at Newcastle, New South Wales, in 1915, joining the 55th Infantry Battalion as a private.
The battalion arrived in France on 30 June 1916, and proceeded almost immediately to the frontline at Fromelles, which was a disastrous battle for the Australian forces. In 1917 and 1918 the battalion was engaged in the 2nd Battle of Bullecourt, the Battle of Polygon Wood and the defense of Villers-Bretonneux.
He was killed in action in France on 17 August 1918 and is buried in Cerisy Gailly Military cemetery. His name is located on panel 160 in the Commemorative Area at the Austalian War Memorial.
There is a problem with the records for his son. Both the birth and death records give the father as Walter J (not S) Caldwell. As I have worked from transcripts and have not seen images of the documents the relationship between Walter Scott Caldwell and the child Walter J Caldwell cannot be regarded as definite. See also Newcastle Morning Herald and Miners' Advocate (NSW 1876 - 1954) Death of Walter Caldwell.
(CALDWELL - Passed away April 6 and Roxburgh Street, Stockton. Walter James Caldwell, son of Private Walter and Mrs. Caldwell. Aged 3 months. -- At rest).
Commonwealth War Graves Commission Private CALDWELL, WALTER | Service Number 1286A | Died 17/08/1918 | Aged 24 | 55th Bn. | Australian Infantry, A.I.F. | Son of James and Alice Caldwell; husband of Mabel Caldwell, of Edward St., Waratah, New South Wales. Born at Liverpool, England.
Application to enlist in the Australian Imperial Force. Recruiting Depot A.I.F. Newcastle. Accepted 9 March 1916. Age 23 years, 10 months. ::Height 5 ft 6 1/2 inches. Chest measurement, fully expanded was 36 inches. Has a lot of descriptive detail. He had blue eyes and fair hair, tattoos on both arms and a vaccination mark. Also a burn scar on one arm. He sailed from Australia to Europe in 1916. [Australia, WWI Service Records, 1914-1920]
Walter Scott Caldwell Service number 1286A Rank: Private Date of death 17 August 1918 Unit: 55th Battalion (Infantry)Service record
See Roll of Honour at www.am.gov.au Service No 1286A, Private in 55th Battalion Infantry. Killed in Action. Age 24. Residence at time of death Edward St. Waratah. Australian War Memorial
Killed in Action in France and buried in Cerisy Gailly Military cemetery. Gravesite Details. Private, 55th Battalion, Australian Infantry, A.I.F. Killed in action. Son of James and Alice Caldwell; husband of Mabel Caldwell, of Edward St., Waratah, New South Wales. Born at Liverpool, England. Age: 24. Plot I. A. 18. MEMORIAL ID 56445389. Find a grave index
It may be possible to confirm family relationships with Walter Scott by comparing test results with other carriers of his ancestors' Y-chromosome or mitochondrial DNA.
However, there are no known yDNA or mtDNA test-takers in his direct paternal or maternal line.
It is likely that these autosomal DNA test-takers will share DNA with Walter Scott: