Casanova's winning Military & Lace look. Photo: Barbara Nitke / Lifetime Television.

With 12 "Project Runway" designers left in the competition, the judges set up a group challenge to see how well the contestants play with others.

Naturally, that's where things start getting really dirty, so much so that Tim Gunn is forced to end the episode with an epic tongue lashing.

And sew it goes:

The Challenge: The dozen contestants have to split into two groups of six. Last week's surprise winner Michael Costello (see his winning look here) assembles a team consisting of fellow challenge winners Gretchen Jones and Andy South, along with Ivy Higa, A.J. Thouvenot, and Christopher Collins. The other team has not a win under its belt and is made up of underdogs April Johnston, Peach Carr, Michael Drummond, Valerie Mayen, Mondo Guerra, and Casanova.

The Twist: Gunn tells the designers they will be working on a cohesive six-piece collection that is on trend for Fall 2010. Each collection must revolve around one concept (minimalism, ladylike '50s silhouettes, menswear for women, or military) and one textile (metallic, camel, leopard and cheetah print, plaid, or lace), and the groups get $1,000 to make it work. The underdogs choose the seemingly contradictory theme of military and lace, while the other team goes for menswear as women's wear rendered in camel.

The Workroom Drama: Two-time winner Jones hijacks the leadership role on Team Luxe, and the rest of her group (save for Costello, perhaps) are more than happy to be her devout followers. After all, she's won two challenges! Things start to get ugly when the entire team makes it clear they don't respect Costello -- despite his episode 4 win -- by questioning his proficiency (to his face!) in making a cowl-neck top and criticizing any garment he touches.

Over on Team Military & Lace, Casanova is told by Gunn that his black lace blouse is looking matronly (the kiss of death!) and "needs to be youthened up." The designer, who wears an unfortunate lime-hued deep V-neck sweater through most of the episode, has an expletive-laced meltdown and flings himself on the couch outside the workroom until his model coaxes him back.

The Guest Judge:
Marchesa's Georgina Chapman (who announced her pregnancy this spring) sits pretty and is polite overall.

Who's In:
Perhaps even a surprise to themselves, Team Military & Lace is deemed the winner, with the garments made by uber-underdogs Carr and Casanova rounding out the judge's favorite looks. Heidi Klum even calls Casanova's lace top (the same one Gunn disliked), "Super-chic and hot. I want to be that girl." For his work on the sexy lace top and skinny cream-colored military pants, Casanova wins the challenge.

Who's Out: In a cringe-worthy, nine-minute critique of Team Luxe, Jones -- who, despite being a solid designer, gets more and more repulsive every time she opens her mouth -- starts out defending the collection, even breaking into tears of pride. Costello, Higa, and Thouvenot also blink away wet eyes. "It's like having a baby and someone saying it's ugly," Higa tells the judges through tears. "I think it's beautiful."

After hearing more of the judges' comments, Jones suddenly turns on her team and throws Costello (who has immunity!) under the bus, and the other designers follow suit. In the end, Jones and Thouvenot head to the chopping block, with Thouvenot eventually going home due to what Michael Kors describes as an "ill-fitting flight attendant shirtdress."

The Aftermath: So upset by the schoolyard cruelty -- which causes Costello to cry -- Gunn charges backstage and delivers the business: "I have a few words for Team Luxe. I fundamentally do not understand your behavior and demeanor and effect on the runway. I don't get it. I don't know why you would let Jones manipulate and control and bully you. I don't understand it. And A.J. you've taken the bullet."

And so the plot thickens...

In related news, check out Heidi Klum's bikini body!