115. The Longest Night  

As The Prince of Darkness continues his murderous rampage across California, the BAU go after him to save Detective Spicer's daughter from him.  

After Morgan and Detective Matthew Spicer are ambushed, the BAU continues their search for the "Prince of Darkness" to retrieve Spicer's daughter, Ellie, and stop his killing spree once and for all. When they get into a stand-off with the UnSub, JJ is forced to negotiate for Ellie's freedom.  

116. JJ ... While trying to get two suspects to reveal what they've done with a missing woman, the BAU brace themselves for the loss of one of their own. 

When JJ attempts to reunite a family whose daughter has mysteriously disappeared, she deals with a new job offer that she can not ignore. Meanwhile, the BAU braces for the loss of one of their own. 

Last appearance of Jennifer "JJ" Jareau as a series regular until season seven.  

117. Remembrance of Things Past 

The team is still adjusting to the loss of JJ from the unit, she who was transferred to the Department of Defense against her own wishes. The BAU's next case takes them to Bristol, Virginia, where young blond women are abducted from highly public locations. They are tortured and sodomized before being murdered by electrocution, their bodies dumped in a common They were forced to telephone a loved one to tell them of their impending death. This case is reminiscent of a sixteen year old cold case that Rossi worked on, the unsub of the cold case nicknamed the ...

 Rossi believes that an old murderer with Alzheimer's, whose case has haunted him for 25 years, has appeared again after several women are found dead in the same manner.   

118. Compromising Positions 

The BAU travel to Akron, Ohio, where two sets of married couples have been murdered in the span of a week. The husbands, who had Viagra in their system but who were not prescribed the drug, were shot while the wives were stabbed. The couples were forced to have sex with the husband wearing a condom, before they were killed. In reviewing the crime scenes, Morgan and Prentiss determine that the unsub is not a sexual sadist as he was trying to set a romantic mood for the kills, and is compensating for a probable recent bout of impotence. In interviewing the victims' ...

The BAU travels to Akron, Ohio to investigate a series of murders on couples, who are forced to have sex before being murdered. Meanwhile, Hotch looks for someone to fill JJ's role on the team.  

119. Safe Haven 

Two families consisting of a mother, father and two children are murdered in two consecutive days in the Iowa/Nebraska border area. The children are strangled, the mothers killed by blunt force trauma and the fathers stabbed multiple times. The father in the second set of murders was also eviscerated crudely postmortem, meaning that it was done not as torture but rather out of curiosity. The autopsies show that the mothers suffered the most pain in their deaths, making the BAU believe that the mothers are the key to the unsub's rage. In reviewing the crime scenes, the...  

The BAU team is called in to investigate the murders of entire families. Profiling becomes a somewhat difficult task for the team after knowing that each member of the family is killed differently than the next. Also, Morgan receives a visit from someone unexpected. 

120.Devil's Night  

The BAU go to Detroit to catch a man who burns his victims alive during the pre-Halloween celebration Devil's Night.  

 After several people are found burned alive once a year before Halloween, the BAU is called in to Detroit to investigate. The team later finds out that the victims chosen by the unsub are not random.
Recurring character: Cade Owens as Jack Hotchner   

121. Middle Man 

In separate incidents, three exotic dancers have been found dead in corn fields in Johnson County, Indiana. The women were abducted following their shift at work on a Friday night, and killed sometime at the end of the weekend on Sunday. The latest victim, Meredith Joy, had the DNA of two people under her fingernails, meaning that there are at least two unsubs. In reviewing the site where Meredith's body was found, Morgan and Rossi determine that there are probably three unsubs who are locals since they seem to know the area well. Another dancer, Stephanie Wilson, has...  

When the bodies of exotic dancers are found murdered in the corn fields of Indiana two days after being kidnapped, the BAU must race against time when they realize they only have two days to find the latest victim who has just been kidnapped. The unsub's true nature is revealed after he watches the reports of his killings on the news.   

122.  Reflection of Desire  

Twenty-something Kelly Landis, who has been missing for three days, is found dead in a back alley in Georgetown. Although the D.C. police don't connect her death to any other murders, they call in the BAU because of what was done to her: her lips were cut off. The unsub wants press on the murder as he sent a photograph of Kelly to one of the Georgetown area newspapers. The BAU believe the unsub to be local and that the police have already interviewed him. Based on finding a homeless man living at the crime scene, they determine that the unsub is the man who reported ... 

After Kelly Landis, a woman missing for three days, is found dead, the BAU is called in when the D.C. Police cannot connect the death to any previous cases. They call in the BAU because of the unsub's style of killing: cutting off his victim's lips. The unsub is easier to identify after Garcia reveals some of her personal life.  

123. The BAU team has to go deep into the forests of the  Appalachian Trail after a young boy is found murdered there. The unsub appears to be a man who targets young boys in the wilderness.  

124. The BAU searches for a killer targeting women in Las Cruces, New Maxico.  Meanwhile, Hotch looks into a FBI trainee with an interesting past to help them out during the investigation.  

First appearance of Rachel Nichols as FBI Cadet Agent Ashley Seaver.   

125. Morgan testifies that a man should be released on parole but regrets his decision when, only days later, the man kills somebody. Things turn out to be not so simple.
Recurring character: Jayne Atkinson as Erin Strauss
Note: Thomas Gibson does not appear in this episode.   

126. As the BAU investigates a series of ritual murders in Miami, one team member finds their health being compromised.   

127. Two young lovers embark on a murder spree in Montana that sends the BAU team to investigate and stop them before they kill again. Also, Prentiss receives shocking news from her previous boss at Interpol. 

128. The BAU is summoned to Los Angeles to investigate a series of unusual murders and Prentiss sheds some light on her past before she joined the BAU. 

129. As the team tracks down a bogus self motivational coach who kills her patients in New York, Prentiss also receives some disturbing news about one of her former colleagues. 

Note: Rachel Nichols is promoted to main character   

130. As Reid tries to make a connection with an autistic child to help in finding the boy's missing parents in  Lafayette, Louisiana, Prentiss enlists two former Interpol colleagues in hunting an old nemesis.
Recurring character: Cade Owens as Jack Hotchner   

131. Prentiss begins to feel the heat after she and Morgan assist in solving a series of suspicious murders that involves Prentiss's old Interpol nemesis, Ian Doyle.   

132. As Prentiss faces off against her sworn enemy, Ian Doyle, the BAU call in JJ in the hope that she can help them find Prentiss and capture Doyle before it's too late. Although JJ later tells the team that Prentiss is dead, it's actually revealed that Prentiss is still alive and that she faked her own death before going into hiding with only JJ and Hotch knowing. 

Last appearance of Paget Brewster as Emily Prentiss until season seven. 

Guest star: A.J. Cook as Jennifer "JJ" Jareau  

133. The BAU is called to Portland to assist in catching a pack of killers who enjoys targeting victims.   

134. As the BAU investigates targeted killings in Tampa, they deal with their own feelings about the loss of Prentiss.

135. The BAU hunts a stalker in San Diego who is targeting college students. Meanwhile, the team comes under Strauss' scrutiny in the wake of the loss of Prentiss.
Recurring character: Jayne Atkinson as Erin Strauss   

136. The BAU is called to a North Carolina resort town after a woman is found badly injured and another woman is missing. On arrival, the team discovers these two women are not the only victims.
Recurring character: Cade Owens as Jack Hotchner  

137. The discovery of bodies buried in the ocean floor off Jacksonville prompts the BAU to intervene; Morgan's aunt suspects her missing daughter may be among the dead.
Guest star: Denise Dowse as Yvonne Burns  

138. The team tries to close the most challenging case involving two bodies and a human trafficking organization. In addition, Hotchner warns the team of possible changes in the team while a surprise team member returns.  

Final appearance of Rachel Nichols as Ashley Seaver. 

Guest star: A.J. Cook as Jennifer "JJ" Jareau