Shortly after his return to England Johnstone accepted a mastership in Modern Languages at the Edinburgh Academy, where his elder brother had been a classical master for some years. He came into residence in September, 1890, and Edinburgh was his home until he left that city for Manchester, in January, 1896. On the whole he was happy there; for though teaching foreign languages to boys is rather a thankless task, he was cheered from time to time by the successes of his pupils in examinations elsewhere, mainly those for entrance to Woolwich and Sandhurst. He could even confess, after a long summer holiday on the Continent, that "he was again thoroughly penetrated with the atmosphere of gray old long-faced Sawbath-keeping Edinburgh." After all, Johnstone, though he considered himself an Englishman, was, as may be gathered from his name, Scotch on his father's side; his mother, too, had a strain of Scotch blood. So perhaps that quiet self-contained manner and all that it implied came to him from north of the Tweed. About this time, he was penetrated with the excellent purpose of training his bodily nerve. He knew that he could never be noticeably muscular, or anything more than wiry, with his light frame and high tension. But he would say, "we ought to be able to see a man fall from a high scaffolding on to the pavement, just before our feet, battered, and to do whatever is necessary without turning a hair." Accordingly, though himself most sensitive to pain and to the sight of it, he fraternised with the young doctors and surgeons whom he met, accompanied them to operations, watched the worst things, and even gave his help, which was more than once invited owing to his deftness and neatness of handling. In this way he got over any shrinking of the nerves. In Edinburgh he also managed to find some amusement. He was a foreigner in his adaptiveness to restaurant life, and found a quiet French café to his taste, where he took his visitors. The odd stratification of Edinburgh society into the various aristocracies of the country, University, professions and commerce, and its broad Scotch democratic feeling, entertained him. He was in one emergency summoned as French interpreter in the police court, and was pleased at having given satisfaction to himself and the magistrate, as the case was a somewhat delicate one and demanded nicety of expression. York Powell, writing to a friend in June, 1893, spoke of Johnstone as "a fine fellow, very interesting; a musician doomed for the sins of others (for he is not a great sinner) to be a dominie in Edinboro', where he is consoled by an old Frenchman who can talk and understand; and they have, with one or two more, a little French club. Each pays sixpence a night for expenses, and you have simple refreshments and sound conversation."