Sister Agnes Carson is a non-canonical character created for the 2009 ITV adaptation of Nemesis. She is one of two nuns on the "Daffodil Motor Coach Tours" which Jason Rafiel had arranged for Miss Marple. She and her companion on the tour Sister Clotilde Merryweather were both formerly based at St. Elspeth's Convent. Sister Agnes is the older and senior of the two nuns and had the title of Mother Superior, although for some reason she is listed in the passenger list as Sister rather than Reverend Mother or Mother Superior. The convent of St Elspeth is near Medhurst, a village which is one of the stops on the itinerary of the tour. By the time of the tour, the nuns of the convent had moved to London and the buildings at St. Elspeth had been abandoned. Sister Agnes is portrayed by Anne Reid.
Jason Rafiel had asked Miss Marple to solve a possible crime or put right an unknown injustice. Through the course of events in the tour, it becomes apparent that the crime or injustice has to do with the fate of a young girl named Verity Hunt. It also becomes apparent that all the passengers in the bus (which Rafiel contrived in various ways to bring on to the tour) are somehow linked to the girl. Sister Agnes Carson is no different. She tells Miss Marple that during the war, a German pilot had been shot down near the convent. The nuns sheltered the injured pilot and tended his wounds but did not report him to the authorities. Verity Hunt was at that time a novice at the convent. She and the pilot fell in love and they planned to run away together and escape to Ireland. So the Mother Superior believed, Verity was convinced to pray for strength and reject the pilot. However, shortly after the pilot escaped from the convent, Verity also disappeared. The pilot was captured but Verity was never seen again. The Mother Superior reported Verity's disappearance to the authorities but did not mention the German pilot. The Mother Superior told Miss Marple she believed the German pilot killed Verity, probably in a fit of rage after hearing that she turned him down.
One of the fellow passengers on the tour turns out to be a German and a former pilot. Although he calls himself "Michael Faber", the Mother Superior recognised him as Michael Rafiel, the pilot that the nuns had sheltered in the convent. When she met him, the Mother Superior was heard to say to her companion that "old sins cast long shadows".