Borders of Infinity, written by Lois McMaster Bujold and published in 1989 by Baen Books, is a collection containing "The Mountains of Mourning", "Labyrinth", and "The Borders of Infinity", together with a very short tale wrapping them together. The Reader's Chair audiobook edition, published in 2000, was read by Michael Hanson and Carol Cowan.
Borders of Infinity came in sixth place for a Locus Award in 1990.
Timeline of framing story
Miles had returned to Barrayar severely injured from a mission to rescue Barrayaran citizens from mercenary hijackers. Shortly after he underwent surgery to replace his shattered arm bones with synthetics, Simon Illyan paid him a visit. It turned out that he was suspected of peculation because of how expensive the events of two of his missions had turned out to be. Illyan believed that the accusations were politically motivated as a plot against Aral Vorkosigan; Miles told him the full tales of the two missions so that Illyan could defend him against the accusation.