Although he had thus extraordinarily succeeded in escaping from jail, it was not long before he was again secured for a new offence, committed in company with his old companion M'Guire, whom he had met at Dumfries. While the latter, however, was again convicted and received sentence of transportation for fourteen years, the former again obtained his liberation from prison, but under circumstances which eventually cost him his life. He was detained in the jail of Dumfries, and a fellow named Laurie, who was confined in the adjoining cell, suggested to him the possibility of their making their escape, by knocking down the jailor and taking the keys from him. Haggart, however, opposed a scheme, which he deemed unnecessarily violent, for he had already made arrangements, by which he hoped to secure his own safety; but another prisoner, named M'Grory, who was under sentence of death, urging the absolute necessity of violent means, he consented to seize and gag Thomas Morrin, the head turnkey, and to take his keys from him, and then to open the doors for all the prisoners to fly. Laurie, however, still persisted that they should use violence, and he employed a debtor, who was in the same jail, to procure him a large stone, with which he expressed an intention of attacking the jailor; and it appears that Haggart now agreed to his proposition. Hunter, the keeper of the jail, having gone to the races, it was determined to seize the earliest opportunity, and Simpson and Dunbar, two other prisoners, were made acquainted with the plot. M'Grory's irons having been removed, Morrin was called up on some pretended errand, and Haggart immediately burst upon him. He struck him one blow with the stone, dashed him down stairs, and without the loss of a moment, took the key of the outer door from his pocket. Dunbar picked up the stone, but it appears that no more blows were given, although Morrin received some other wounds in falling.
Dunbar was standing over him, apparently rifling for the key which Haggart had already secured, Simpson had hold of Morrin's shoulders, and was beating his back upon the stairs, when Haggart rushed past them, crossed the yard as steadily as he could, took out the key, and opened the door. On getting out he ran round great part of the town; Dunbar overtook him, and at that moment they saw an officer coming directly up to them. They wheeled round and ran, but in a moment Haggart had the mortification of seeing his fellow-adventurer secured. He at first thought of rushing in to rescue him, but the crowd was too great to allow him to make the attempt; so he consulted only his own safety, and ran nearly ten miles in less than an hour. He then got on the high road to Annan, when he saw a post-chaise at full gallop almost within twenty yards of him; upon this he threw off his coat, and leaped a hedge into a field where some persons were employed in digging potatoes. They all joined the officers who had got out of the chaise in pursuit of him; but he fled across the field with amazing speed, and made for Cumlangan wood. The pursuers followed him into the wood, but he kept concealed close to the edge, and although they were very near him, he thus eluded their pursuit.