Being now left without an associate, Haggart returned to Newcastle, where he resided for four months, in the house of his old friend, Mrs. A----. During his stay there, one of the young ladies was married to a respectable shopkeeper, when Haggart took the lead in conducting the festivities of the wedding. One evening, having accompanied one of the Miss A----'s to the theatre, on their return, a gentleman much in liquor attempted to insult the young lady; struggling in her defence, Haggart contrived to pick the pocket of his antagonist of nineteen guineas, with which he escaped unsuspected. At length having, as he conceived, remained as long as was expedient in this place, he took his departure in the month of June, and he then proceeded to Edinburgh, where he pursued the occupation of a shop-lifter. At this time, it appears, that he was suddenly seized with a severe and dangerous fit of illness, and being struck with remorse at his past conduct, he returned to the house of his parents; but he was soon after apprehended on a charge of shop-lifting, of which he had been previously guilty, and being sent to jail, all his determinations to be more circumspect and honest, were put to flight. On his release he joined one of his fellow prisoners, named Graham, and with him recommenced the system of plunder, by means of which he had before supported himself.
Having stolen a pedlar's pack, and several articles of linen drapery and hosiery, Haggart assumed the character of a pedlar, and travelled the country to dispose of his ill-gotten goods. After this he returned to Edinburgh, where he remained till January 1820, committing depredations of every description. On the 1st of March he was arrested at Leith, in company with an accomplice named Forest. The offenders made a desperate resistance, but were at length secured and committed for trial. The confinement was too much for our hero, however, and on the evening of the 27th of March, having obtained a small file, he cut the irons from his legs, and then forced up the door of his cell, and got into the passage. He next set to work upon a very thick stone wall, through which he at length made a hole, and got on the staircase just as the clock struck twelve. He had still the outer wall to penetrate, on which he fell to work with great caution, lest he should be heard. Having made considerable progress, he returned to the room where his companion Forest was, and brought him to his assistance; he also awoke one of the debtors whom he knew, and obtained his assistance in removing his handcuffs, having all along been working with them upon him. After great labour and violent pain they succeeded in wrenching the chain in two pieces. He then renewed his operations on the outer wall, and, having removed a large stone, got out a few minutes before five o'clock in the morning. When he gained the outside stair he saw a man coming towards him, and, supposing him to be an officer in pursuit of him, he leaped over the back of the stair; but recollecting that Forest had yet to get out, he prepared to give the man battle, lest he should attempt to seize Forest; but the man said to him, "Run, Haggart, run; I won't touch you." Forest then came out, and he took hold of his hand, and ran off at full speed, pulling him along with him.