After deciding to celebrate Brody's birthday in style, The Hills gang piles onto a private plane heading to Cabo San Lucas, Mexico. The party starts right away when Brody, Doug, Frankie and Justin raise their beers in a rowdy toast as Lauren and Audrina clink their glasses and roll their eyes.When Frankie wonders why Audrina is giving Justin the cold shoulder, she explains that they're not together anymore and he's hoping to hook up with other girls in Cabo. Then, Frankie asks where her new boy Cory is, and Justin cranes his neck to eavesdrop.In Cabo, everyone marvels at the sick villa they have ... until it's revealed that Audrina and Justin are sharing a room. Audrina says no way, so Lauren invites Audrina to crash in her room. As Audrina turns on her heels, she realizes that leaving Justin alone in the room means that he'll most likely have another girl in there to fill the void. Leaving their worries behind, Lauren and Audrina run down to the beach with drinks in hand as Justin watches them frolic in the water.Hanging in the pool together, the boys start dishing about Audrina, and Frankie reveals that she's dating Cory because he treats her right, unlike Justin. In response to that, Justin lets out a big "whatever," annoyed that she's giving him a hard time for seeing other girls when she's dating other guys. To smooth things over, Doug announces that all girls are "shady" as Justin takes another peek at Audrina on the beach.Meanwhile, Heidi and Stephanie are out shopping in The Hills when Stephanie reveals she has a new boyfriend, Cameron. Still, she's a little bummed that she's not in Cabo San Lucas with the rest of the gang. But clearly she knows she wasn't invited because she doesn't get along with Brody -- and she's not quite sure what's going on between her and Lauren. To cheer Stephanie up, Heidi suggests a double date. Stephanie says she's scared that Spencer will be mean to Cameron, but she reluctantly agrees.While having dinner on a patio in Cabo, Audrina shows off a flower in her hair. When Justin asks where she got it, she says Cory gave it to her. After he asks why she isn't staying in the room with him, the tension rises as Audrina reminds him that he wanted to play the field. As she turns her back to him, he mouths to Doug that he's officially free to use his "hall pass." But will he?After Frankie gives a toast, Doug says he has a big surprise for Brody. Lauren guesses that he's invited "sleazies." And she's right! A dozen bikini-clad girls pile onto the patio. Soon, the boys and girls start pairing off, leaving Lauren and Audrina alone to chat. Lauren thinks Audrina should talk to Justin about her new boy Cory. But Audrina is clearly torn; being around Justin is making her wonder if she made the right choice. When Lauren and Audrina rejoin the group to go swimming in the pool, the party is in full swing and Justin seems to be having a good time with the new girls.Back in The Hills, Heidi and Spencer wait for Stephanie and Cameron, who are late for dinner. On the way in, Stephanie warns Cameron that she and Spencer don't really get along. As soon as they sit down, Spencer rips into them for being so late. Then, he proposes a toast to meeting Stephanie's "first real boyfriend." As if that's not embarrassing enough, Spencer starts to grill Cameron. When Stephanie's new boy admits he used to hang with Brody, Spencer quickly points out that his sister recently "dated Lauren's boyfriend" Doug. Awkward!In Cabo San Lucas, Justin polishes off a beer in the pool. When Audrina drops the flower Cory gave her in the water, he quickly scoops it up. She demands it back but he just taunts her with it. When he swims over to give her a hard time, she walks away and flips him off.The next day, Justin is still flaunting the flower when he runs into Audrina in the kitchen. She tries to get Cory's gift back again but he refuses to let it go. Audrina brings up the fact that Justin came to Cabo on a "hall pass," and he counters that he knows she's been dating Cory. She admits that she left Justin for another guy, but only because he refused to be exclusive.At the same time in The Hills, Stephanie confronts Spencer about his bad behavior the night before. He claims he was just reacting to them being so late. But Stephanie thinks it went beyond that, questioning why he brought up her date with Doug. Spencer finally admits he gave Cameron a hard time because he used to hang with Brody but still thinks Stephanie should be more appreciative of how he treats her. After all, he did pay for dinner. When Stephanie asks Spencer to be nicer, he demands that she be more loyal to him. That's a fair trade, right?Back in Cabo, Lauren and Audrina are having yet another heart-to-heart. Lauren thinks Audrina shouldn't even be talking to Justin, but Audrina reveals that it's hard to ignore him because she still loves him. Lauren doesn't think Justin will ever be the boyfriend Audrina wants him to be, prodding her to let him go. But Audrina doesn't look too convinced.