Plum had been born in 1870 in Dundee's Hilltown. In fact he, although his father was a ploughman from Inverarity turned Dundee docker, and his mother from Monikie, would spend his entire youth in the district, starting football, that is before at the age of eighteen joining East End, with, from one source, Rockwell High School and from another, Rockfield. Both are theoretically possible. The school is still there, as is Rockfield Street but, since he in 1897 he is recorded as a Slater's Helper i.e. labourer school much beyond twelve seems unlikely. His first spell at Dundee would then take him to 1896 and more or less to his prime. The move then to Sunderland therefore is understandable. But he would not tarry long, months only, with the same then spent at Burnley. More might have been expected but there was probably a reason. The footballer cum slate-worker returned to Dundee to marry, his bride Janet Sim, with whom he would have four children, three surviving, all boys including twins. 

Thus it was that after the wedding the couple would be given a year together until what might be considered an early example of international club cooperation, even of nursery clubbing. In 1898 Brighton United out of almost nowhere joined the Southern League. It did so with a constructed team that included at least nine Scots, probably more, including six from Dundee. Plum Longair was amongst them. But, whilst the scratch team finished safely mid-table, the club was clearly under-funded, the Dundee players returning when at the end of the season the money ran out.