The team heads to Yakima, Washington when the remains of a dozen people are found along a creek bed.

While Rossi conducts a profiling course on his birthday, he receives a call from his nemesis Tommy Yates, who discloses the location of his latest victim.

The team investigates a series of home invasions in San Diego involving casualties.

Reid has returned from Houston, where he was visiting his mother who is in a new facility on an experimental drug program. He is called back home from the office while the rest of the team heads off on their next case. It isn't until the team is in the air that they learn that Diana is no longer in the Houston facility, but that she is now living with Reid, as the trial drug was not having the intended effect. Reid had received professional advice that his mother should be in a facility both for her and his own good, but it may be news from a more caring rather than clinical voice which may carry more weight with him. Regardless, he makes himself available to the team, who are in the Tampa, Florida area where two individual deaths have occurred, both now considered murders, the two tied together by ink drawings on the inner arms of the victims, the second victim's whose has one more stroke of the pen than the first. The M.E. is able to determine that the markings were made with the same pen. The death of the first victim, a model suburban soccer mom, was initially ruled a suicide from an overdose of sleeping pills, her own prescription. The second victim, a homeless man, died of a heroin overdose, he who was known not to be a drug user, but rather an advocate for the homeless to get those in need into drug rehab programs. As such, they were both killed using the tools of their life, they presupposing that the unsub forced them to kill themselves. With two subsequent victims, the team also gathers more evidence: that the victims post-mortem were taken to outdoor sites with disturbed ground, and the unsub is connected in some way to fire. The identification of the ink markings in relation to the aspect of the disturbed ground may provide the key to finding where the unsub will strike next.

The BAU investigates the case of a killer who dismembered their victim before dumping just the torso.

When a member of the BAU gets in trouble in Mexico, they enlist the help of the International Response Team.

The BAU investigates a series of pedestrian deaths while a teammate's fate remains uncertain.

A series of acid attacks draw the BAU to Philadelphia, while Reid adjusts to a new reality.

A mother comes forward with information to help the BAU in their investigation of an unsub called the Bone Crusher.

The BAU suspects that two unsubs are operating at the same time when victims killed in different ways are found in the same city.

The BAU investigates an urban vampire who kidnaps his victims at night and holds them underground in the sewer system; Reid makes a difficult decision in prison.

Three victims are found tied to stakes in the Arizona desert.

The BAU investigates when several federal government employees, including a close friend of Walker's, succumb to symptoms of a heart attack; Reid anxiously awaits his trial date.

When Reid fears his mother has been abducted, he asks the BAU to investigate while he's stuck in prison.

Derek Morgan brings the BAU a lead in the case against serial killer and escaped convict Mr. Scratch.

The BAU investigates when several federal government employees, including a close friend of Walker's, succumb to symptoms of a heart attack; Reid anxiously awaits his trial date.

The team investigates a series of home invasions in San Diego involving casualties.

The BAU investigates an urban vampire who kidnaps his victims at night and holds them underground in the sewer system; Reid makes a difficult decision in prison.

The team heads to Yakima, Washington when the remains of a dozen people are found along a creek bed.

While Rossi conducts a profiling course on his birthday, he receives a call from his nemesis Tommy Yates, who discloses the location of his latest victim.

Reid has returned from Houston, where he was visiting his mother who is in a new facility on an experimental drug program. He is called back home from the office while the rest of the team heads off on their next case. It isn't until the team is in the air that they learn that Diana is no longer in the Houston facility, but that she is now living with Reid, as the trial drug was not having the intended effect. Reid had received professional advice that his mother should be in a facility both for her and his own good, but it may be news from a more caring rather than clinical voice which may carry more weight with him. Regardless, he makes himself available to the team, who are in the Tampa, Florida area where two individual deaths have occurred, both now considered murders, the two tied together by ink drawings on the inner arms of the victims, the second victim's whose has one more stroke of the pen than the first. The M.E. is able to determine that the markings were made with the same pen. The death of the first victim, a model suburban soccer mom, was initially ruled a suicide from an overdose of sleeping pills, her own prescription. The second victim, a homeless man, died of a heroin overdose, he who was known not to be a drug user, but rather an advocate for the homeless to get those in need into drug rehab programs. As such, they were both killed using the tools of their life, they presupposing that the unsub forced them to kill themselves. With two subsequent victims, the team also gathers more evidence: that the victims post-mortem were taken to outdoor sites with disturbed ground, and the unsub is connected in some way to fire. The identification of the ink markings in relation to the aspect of the disturbed ground may provide the key to finding where the unsub will strike next.

A series of acid attacks draw the BAU to Philadelphia, while Reid adjusts to a new reality.