The Inner Fight

The mysterious vessel begins targeting former Starfleet officers and the Cerritos is assigned to locate and protect former cadet Nick Locarno. Mariner, whose destructive behavior concerns Freeman, is assigned to a simple repair job near Sherbal V with Tendi, T'Lyn, and Boimler. The Che'Ta destroys their shuttle and they transport to the planet, where they find the senior officers of the missing ships stranded as victims of mutiny: their lower decks officers all planned the attacks with the mysterious vessel. Mariner fights with Che'Ta captain Ma'ah until they are forced to take shelter from a storm. Mariner reveals that she lost a friend, Sito Jaxa, to a Starfleet spy mission and has been acting out over concerns about her new role within Starfleet. Ma'ah helps bolster Mariner's belief in herself and Starfleet.

Summary from Wikipedia, CC BY-SA 4.0.