Risa

Well no actually. In that episode he tells Bashir at least three different contradictory stories. Though right before Garrak thinks he's about to die he tells Bashir that he was really ashamed because he fucked over his best friend and we're lead to believe this is the actual final truth. Then you later find out the friend's name he gave Bashir was actually just Garrak's own first name and that every story Garrak told was a likely a complete fabrication. In the end we know nothing more definitive about him or why he's at the station.