At the beginning of March, Governor Semple went west to inspect the forts on the Assiniboine, Lake Manitoba, and Swan Lake, leaving Robertson in command. On the 16th, suspecting a plot on the part of Cameron and his North-Westers, Robertson intercepted some letters, which transformed suspicion into conviction. He therefore attacked the North-West post, took Cameron prisoner, and removed all the arms, trading goods, furs, books and papers, to Fort Douglas.[101] He furthermore informed his enemy that being situated at the confluence of the two rivers, the Red and the Assiniboine, Fort Gibraltar was the key to the position, and could be in no other hands but those of the lords of the soil. Following up this move, Robertson attacked the North-West post on the Pembina River, captured Bostonnais Pangman, who was in charge, with two clerks and six voyageurs, who were afterwards incarcerated in Fort Douglas. Pursuing his advantage an attempt was made to carry Fort Qu'Appelle. But McDonell, who was in command there, displayed considerable force, and caused the Hudson's Bay people to retire. About this period five flat-bottomed boats belonging to the Company, laden with pemmican and from thirty to forty packs of furs, under charge of James Sutherland, were _en route_ to Fort Douglas. McDonell was advised of the circumstance and seized the whole, while retaining two of the factors, Bird and Pambrun, as prisoners. A canoe was given Sutherland and the others, together with a scanty supply of pemmican, and they were allowed to continue their journey to the fort. On receiving intelligence of this proceeding, as well as of the plots being hatched by the half-breeds and their allies in the West, Robertson concluded that Cameron would be best out of the way; the prisoner was accordingly sent off under guard to York Factory, from whence he reached England seventeen months later. Here he was released without a trial, and soon afterwards returned to Canada, where he spent the remainder of his years. The enemy were no sooner out of Fort Gibraltar than Robertson had the walls pulled down. All the useful material was rafted down the river to Fort Douglas, where it was employed in new erections within that post. [Sidenote: Plan to exterminate the Red River Settlement.]