The BAU is asked to re-open an investigation into the case of a convict - Sam Russell -  who is sitting on death row, convicted of the serial killings of prostitutes ten years ago.  The request came about as a result of political heat generated by a hacker group called "Star Chamber", who hacked into government computers and stole data.  They did so because they were convinced that Russell is innocent.   Garcia was once part of that group, and so she faces her old flame who heads the group - Shane Wyeth - in order to get the convict's file back. Meanwhile new murders take place, which use the same M.O. as the murders for which Russell was convicted. Hotch and AJ interview Russell in prison and determine that though he is guilty, he wasn't alone with the murders.  They determine that it's his partner who is continuing the crimes, and that he is working with Star Chamber to try and get Russell exonerated.  The Unsub is about to murder Wyeth in order to frame him as the missing partner, but is stopped in time by the BAU.