Larkin served during the Dominion War in 2375. She was assigned to AR-558, a planet that the Federation Alliance had captured from the Dominion, under the command of Captain Loomis. They were assigned to protect the planet's communication array. Other members of the 150-person unit included Commander Parker, Reese, Crewman Kellin, McGreevey, and Vargas.
The team successfully held the location for five months, despite expecting to be replaced in ninety days. Over a hundred of the unit was killed over this time, including Loomis and Parker. Larkin took command.
When Captain Sisko and his crew arrived, Larkin turned over command of the unit to Captain Sisko after relating her frustration about their situation and their inability to get reinforcements. The crew, with Sisko in charge, continued to hold the planet. He sent Larkin with Nog and Reese to scout out the Jem'Hadar's location. Despite Nog's hearing ability to locate the camp, they were located and fired upon. Larkin was killed by Jem'Hadar phaser fire which also knocked down Nog. (DS9: "The Siege of AR-558")