Arissa was the alias assigned to an undercover Idanian Intelligence agent who joined the agency in 2371 and volunteered to infiltrate the Orion Syndicate. Because of the nature of her mission, she had to undergo reconstructive surgery and her memories were replaced, with her original memories temporarily stored in a data crystal. After this identity change, she was known as Arissa, and was left on Finnea Prime without any knowledge of her former life.
There, she became a net-girl, using the dataport installed on her neck. Through this, she met the target of her mission, Draim, a member of the Orion Syndicate, who specialized in blackmail and extortion. She worked with him, tapping into computers to get information about people.
In 2373 she tried to leave the Orion Syndicate, which brought her to Deep Space 9. She impressed Chief of Security Odo with her keen observation of Dabo table manipulation via a graviton emitter in Quark's.
While on Deep Space 9, she tried to contact Tauvid Rem, who had a data crystal for her with information by which she could break free of the Orion Syndicate. Because she could not locate Tauvid Rem, she tried to break into the station's computer, during which she was apprehended by security personnel and brought to Odo for interrogation.
When Odo checked her story they found that Tauvid Rem was dead. Later on, Odo caught her on the Promenade when she broke into the assay office. When asked if she found anything in Tauvid Rem's locker, she showed him a data crystal. In order to protect her, Odo had her stay in his quarters. Since first meeting, both had a mutual attraction for each other, and they spent a passionate night together.
Having possession of the data crystal allowed her to contact Draim and offer it in exchange for her life and an exit from the Orion Syndicate. Draim agreed but wanted her dead and instructed his hit men, Traidy and Sorm, to kill her after the crystal was retrieved. Fortunately for her, Odo and an Idanian Intelligence Officer rescued her from Syndicate assassins. The intelligence officer would reveal to Odo her real identity.
With the help of Doctor Julian Bashir, both her memory and Idanian appearance were restored. She said goodbye to Odo, and confided that, even though she was married, the relationship between him and Arissa was real and she would never forget him. (DS9: "A Simple Investigation")