Russert's apparent disappointments lead her to start a new life in Europe with a French diplomat, and she is gone from Baltimore at the start of Season 5. She appears during that season's finale, having returned briefly to Baltimore to help the squad investigate Felton's death.
Russert's dissatisfaction leads her to start a new life in Europe alongside a French diplomat, and she departs Baltimore at the outset of Season 5.  She makes a brief appearance during that season's finale, returning to Baltimore to assist the team with investigating Felton's death.