In the Sons of Korhal, Mirne served in Darabont's unit. At the Fall of Tarsonis, Arcturus Mengsk ordered Darabont's unit to hold back, contributing to the fall of the planet to the zerg. As a result, his unit was branded a coward, and made to wear a yellow slash on their insignia. Their battlecruiser would not undergo repairs since the attack.
The next year, Mirne was ordered to take the Cyrus to the Ghost Academy, and take a number of ghost trainees to The Baker's Dozen, apparently not being told there were four survivors from the Old Families there. Mirne let the trainees know they she was as unsatisfied with ferrying them as they were.
During their trip, Lio Travski detected the Old Family transmission from Shi. He and other ghosts broke onto the bridge and told Darabont and Mirne. The commodore was initially uninterested until told there were zerg there too. When the distress call mentioned a reward, Mirne stated that it may be worthwhile, and that Mengsk couldn't blame them for what he ordered them to do on Korhal.
The marines landed first on Shi, defeating a wave of zerg. However, they were overwhelmed from hatcheries south of Mandible Canyon. Mirne coordinated the use of Apocalypse-class nukes to of the smaller clusters of hatcheries.
Soon after, the a larger force of zerg from another cluster of hatcheries began to assault the Cyrus. The Cyrus attempted to assault the hatcheries, but was hit by a spore cannon, and crash landed. Darabont and Mirne survived the initial crash, but soon zerg swarmed their ship, and Mirne was devoured by a hydralisk.