In the beginning of 1889 Mr Darling began to show unmistakable signs of failing health. He was easily fatigued, and less able for his wonted tale of service. The landmark and limit of threescore years and ten now stood within sight. The change became more perceptible in November, on the occasion of the death of his brother-in-law, Mr James Bunyan, a man of kindred spirit, who had long been his fellow-worker in all his labours of love. There was now a settled languor which it seemed impossible to throw off. Spring came, with its song-birds and early flowers, and benefit was sought in a change of air and scene, first in Rothesay, in the month of March, where he underwent a course of baths, and then in a short visit to Aberdeen and Inverness, in the midst of relatives and friends; and in the end of April he returned to Edinburgh, with strength increased and appetite improved, and the old looks beginning to return. But before midsummer was far advanced, he again became conscious of decaying strength, his altered looks were ominous, and his family and friends became seriously alarmed. Hitherto the symptoms had only been those of gastric catarrh, but it began to be suspected that something much worse was seriously at work. A consultation of skilled physicians and surgeons was held, when it was feared that the malady was much more deeply seated, and was perhaps irradicable. A long-cherished intention to visit a beloved married daughter, Mrs Murray, and her family, at Queensland, was now finally abandoned. Still a faint hope of recovery continued to be cherished.

Accordingly, towards the end of June, accompanied by Mrs Darling, our patient travelled northward to Inverness, to be present at the marriage of Dr Darling, their only son. In the Highland capital he remained for four weeks, making pleasant excursions to Strathpeffer, Beauly, Glen Urquhart, Nairn, and other scenes of beauty and health resorts. Probably there was no visit which he enjoyed more than one which he made to a large gathering of Band of Hope children at Culloden. Here, under the presidency of Duncan Forbes, Esq. of Culloden, he gave what proved to be his last public address. It was a fit manner of closing his public life. Friends who were present on the occasion, remarked that even his zeal in the cause of temperance was far exceeded by the earnestness with which he expressed his desire that his young hearers would accept Christ as their Saviour, and their Guide and Guardian through the perils of life. Almost all his illustrations were taken from his own experience, and, though very homely, they never "missed fire." Some of his sentences sounded as if they were prophetic of what was coming, and the shadow of death had already fallen upon his spirit.

The month of August was spent by him at Kirkcaldy with his eldest daughter, Mrs Deas, her husband, and family; and the greater part of September at Aboyne, on Deeside, with his eldest and only surviving brother Thomas, who loved him as even few brothers love.