The team travel to Mexico to investigate reports of a serial killer who targets elderly women.Hotch’s hopes for a rare weekend off with his family are dashed when he is called into the office for a briefing.An elderly woman has been murdered in a small Mexican town, and the papers are making noise about the crime being the work of a serial killer – 11 similar murders have occurred in the town over the past two years.The government, however, are keen to dispel the rumours before the town’s tourist trade is damaged, and have called in the BAU in the hopes of writing the murder off as an isolated incident.When the team arrive in Mexico they are greeted by Captain Navarro, the officer assigned to the case by the District Attorney.Gideon warns Navarro that the team can’t predict what conclusion they are going to reach, asking him: “You are aware that we may not be giving you the answer you’re looking for, yes?”At the home of victim Lupe Trejo, the team search for clues.There is no sign of forced entry, indicating that the killer was someone that Lupe knew or trusted, and the presence of two glasses of a beverage traditionally only drunk by women suggests the visitor was female.

However, the fact that Lupe was stabbed in her face, chest and genital area indicates that a heterosexual man was to blame for her murder, as these are the hallmarks of a sexual homicide.

The first suspect thrown up by the investigation is Lupe’s estranged son, Miguel.

He denies hurting his mother, and it looks as if he is telling the truth when Gideon realises that Miguel is gay and therefore unlikely to be responsible for the murder.

When the troubled young man refuses to defend himself by admitting his sexuality, the team attempt to get answers from his sister Rosa.

She tells them that Miguel’s lover, Roberto, was watching the house when Miguel was fighting with his mother.

Could Roberto have killed Lupe because she denied Miguel’s relationship?

After Roberto is questioned, his testimony puts him out of the picture.

However, the team are intrigued by his description of a ‘heavy-set’ female social worker who he saw visiting Lupe.

When DNA tests on the glasses in the kitchen table reveal that Lupe’s visitor was male, the team realise that her killer was probably a cross-dressing man who posed as a woman to gain her trust.

The next step is to present the police with a profile.

The team explain that they are certainly looking for a serial killer, who is a man aged between 35 and 50.

A known sex offender, his sexual crimes have escalated into fatal attacks on women who represent authority figures he hates.

And when another woman is killed, it becomes clear that the killer’s attacks are becoming more frequent.

“He’ll kill again soon,” predicts Gideon.

The important thing is to identify the killer’s ‘stresser’ – what made this man step up from sexual attacks to murder?

When the team begin to research rapes reported just before the murders began, testimony from a local woman named Milagros provides the answer.

She tells them that when she was raped by a man who was wearing a dress, she fought back and mocked him for being ‘a woman’.

The team realise that being humiliated in this way was the trigger – and that this man is not going to stop until he is caught.

When more of the same man’s rape victims come forward, the link between the murder victims is suddenly revealed.

The killer is murdering the mothers of each of his rape victims... in the same order as he raped their daughters.

And as Milagros was the last woman he raped, her mother is next on his list to kill.

The BAU team rush to her house, but are greeted by a sight that suggests the victims have meted out their own bloody form of justice...