Emily Prentiss is the current Unit Chief of the BAU who first joined the team two episodes after Elle Greenaway resigned from the FBI for good. At the end of Season Seven, she resigned from the BAU and accepted a position with Interpol in London. She was replaced by Alex Blake, who held the position until her own departure at the end of Season Nine. The position was then taken over by Kate Callahan for the duration of Season Ten before her own departure. She rejoined the team in Season Twelve and was then promoted to Unit Chief following the resignation of Aaron Hotchner. For a time, she was placed on administrative leave and suspension, pending an investigation by Assistant Director Linda Barnes; her position taken over by Jennifer Jareau temporarily.