Lemec was a Cardassian gul and commanding officer of the Galor-class warship Reklar. In 2369, Lemec was the Cardassian representative in negotiations with the Federation, represented by Captain Edward Jellico. The Federation suspected that the Cardassians were planning on seizing some disputed planets in Federation territory along their mutual border. When Jellico pointed out the Cardassians were building up ships along the border, Lemec retorted that they were simply conducting training exercises.
Lemec was involved in the plot to kidnap Captain Jean-Luc Picard in order to obtain information on Starfleet ship deployments for the defense of Minos Korva. During later negotiations, Lemec informed Starfleet that Picard had been captured on Celtris III. Lemec offered to release Picard into Federation custody and forget about the incident in exchange for an immediate withdrawal of all Federation ships from the sector surrounding Minos Korva; a proposal which was rejected by Starfleet. Jellico subsequently discovered that Lemec and his fleet were hiding in the McAllister C-5 Nebula, from where they were preparing an attack on the disputed territories. Lemec's ship and the rest of the Cardassian fleet were mined by a shuttlecraft piloted by William T. Riker. After laying the mines, Captain Jellico ordered Gul Lemec to retreat after ejecting their phaser coils. With no other choice, Lemec agreed; his fleet left the nebula and Picard was released. (TNG: "Chain of Command, Part I", "Chain of Command, Part II")
In the novel The Battle of Betazed, Lemec was the commander of the Cardassian forces that helped the Jem'Hadar conquer the planet. They were building a Cardassian space station similar to Terok Nor and Lemec hoped to be the Prefect of Betazed, as Dukat had been of Bajor. Lemec was captured during the liberation of the planet. Lemec was also in the Tales of the Dominion War story "The Ceremony of Innocence is Drowned". Lwaxana Troi and other Betazoids sensed Lemec's elation over Cardassia's penetration that far into Federation Territory.