A group women enter a flower shop. A photographer named Ryan Becker approaches them to talk about a wedding. He flirts with them. The bride-to-be (Madison Mills) invites him out to her bachelorette party at the Wolf and the Rose bar. The flower shop owner Nicole Seavers notices Madison touching his arm.
Hotch informs Morgan and Garcia that Giuseppe Montolo has refused his request for an interview at his prison to discuss the identities of "The Dirty Dozen" people who are marked for death.
The BAU are called in to investigate two murders of brides-to-be, whose dead bodies were left in dumpers. Both victims had bride-to-be sashes wrapped around their heads.
The first victim is Brandy Green who was murdered three months ago. Garcia tells the team that Green came to town for a bachelorette party and was left dead in a dumpster. Cause of death was a blow to the head.
The second victim is Ashley Wilcox, who was murdered two days ago. Though she too was left in a dumpster and had been given a blow to the head, her cause of death was strangulation.
There is nothing to connect the two victims except for the fact they were brides-to-be.
Madison Mills is at her bachelorette party at the Wolf and the Rose bar. She goes out to get some fresh air, is hit over the head and then carried away.
Garcia tells the team about Madison Mills, who has now been reported as missing.
Morgan and Lewis interview one of Madison's bridesmaids - Kelly Goodwin. She tells them about a strange man in the bar who raised his voice at Madison.
Garcia tells Morgan she's identified a suspect whose fiancé called off their wedding three months ago. His name is Karl Ulrich.
Rossi interviews Ulrich but later concludes his alibi was solid.
Nicole's sister Dana flirts with Ryan Becker in the flower shop. He leaves with Nicole, and then Dana imagines him professing his love for her. She goes downstairs to where Madison is laying bound and gagged. She imagines Ryan telling her she needs to kill him in order to keep their love pure.
She kills Madison.
The team finds Madison in a tree with the word "slut" written on her forehead. Lewis and Reid conclude that the unsub is female.
Dana flips through a wedding album in which the original faces of the couple has been covered over by cut out pictures of herself and Ryan.
Nicole comes into Dana's room and encourages her to go back to see her doctor. She expresses worry that she's sleeping a lot and doing online shopping. Dana assures her she's okay and doesn't need to take her medication. Nicole invites her out to a special meal with Ryan. Dana gets excited and tells her she'll go.
As Dana gets ready, she imagines Ryan telling her that they will announce their love at dinner that night.
Morgan asks him Lewis about her missing engagement ring. She tells him she doesn't like to wear it while on the job. She tells him that ever since she and Douglas got engaged, women seem more flirtatious with him. It bothers her.
At dinner, Ryan proposes to Nicole. Dana is quietly enraged.
Dana is walking in the street with a knife in her hand. She is approached by imaginary Ryan who tells her his proposal was all part of a game that they must continue to play out before they can be together. He tells her that Nicole tricked him, just like the other girls. He tells her that Nicole is the real threat, and that she must kill her.
Garcia identifies Dana as the likely unsub. She tells the team that Dana has set up a wedding registry for herself and Ryan, and that she's been buying items off the registry and has been sending them to herself, but that as of last night Dana's sister Nicole is engaged to Ryan.
Hotch, Morgan, Reid and Rossi rush to the flower shop and break in. They find evidence of the murders in the basement.
Reid and Lewis suspect from Dana's meds that she has PCOS (Polycystic Ovary Syndrome), a condition that can cause depression.
Morgan and Rossi discover evidence of Dana's obsession with Ryan.
After searching the flower shop and realizing neither Dana or her sisters are there, Morgan and Hotch rush to the flower shop's greenhouse.
At the greenhouse, Dana confronts Nicole. Nicole turns her back on her, while texting Ryan. Dana grabs a shovel and slams it over her head.
She ties her sister up. Nicole wakes up to find Dana standing in a wedding dress. Dana tells her it's her wedding day and that Ryan and her are getting married.
Ryan arrives at the greenhouse. Dana tells him not to come any closer. She holds a knife to her sister's throat.
Hotch talks her down by convincing Ryan to tell her he loves her. He does and she drops the knife. They take her into custody.