Irina Galliulin was a former Starfleet Academy cadet and scientist of Russian descent, once romantically involved with Pavel Chekov
. Irina believed Pavel to have always been rigid and Pavel believed Irina to always have been too free-spirited. The two had several disagreements before they parted ways, each accusing one of leaving the other. When Irina dropped out of the Academy, Chekov left, but came back to look for her, who was at the time staying in the city with friends. Irina eventually joined the counterculture movement of Dr. Sevrin and his search for the mythical planet Eden, while Pavel joined the crew of the USS Enterprise.
In 2269, Galliulin, Dr. Sevrin and four of their colleagues stole the space cruiser Aurora to further their search for Eden, but they were apprehended near the Romulan Neutral Zone by the Enterprise on stardate 5832.3.
During the return trip to a Federation starbase, Galliulin encountered her lost love, the now Ensign Chekov. Initially happy to see one another, Chekov adamantly disapproved of her new lifestyle and attempted to cast her off. Galliulin was coerced by Sevrin to help him commandeer the Enterprise. She visited Chekov, who on assignment to help Spock
locate Eden was working in Auxiliary Control, to apologize for upsetting him. Her ulterior motive, however, was to subtly use him to gain knowledge of the systems of the starship, which were later used by Sevrin for hijacking control of the Enterprise.
Galliulin aided Sevrin in disabling the ship's crew and appropriating the Enterprise shuttlecraft Galileo II, which they used to get to the planet. However, on the planet's surface they discovered that their "Eden" was actually a poisonous planet, and her feet were burned on the acidic grass. Galliulin and three of the surviving followers were transported back to the Enterprise, where they were let off at their previous destination, the nearest starbase.