With one week to go until Evan and Paige's big day, the Hamptons are a winter wonderland (albeit a snowless one) and wedding preparations are in full swing. But before they can say their vows, the lovebirds have to celebrate something else: their last officially single days.

Best man Hank has a tame night in NYC planned for the groom's bachelor party, while DIvya and the bride are set to meet Paige's friends in Aspen for Paige's bachelorette party. But bad weather and the interference of Hank's former nemesis Ken "Killer" Keller mean that both the ladies and the gentlemen are in for a change of plans, and, surprisingly, both parties soon find themselves unknowingly headed to the same place: Las Vegas.

In Sin City, the boys hit the tables while Paige plays cupid and reconnects still-crazy-for-each-other Divya and Rafa, who take their relationship to a new level with an impulsive visit to the wedding chapel. Not long after the groups reunite, it's time to head back to the Hamptons (and reality), where Hank attends to his cousin Owen and Ken's girlfriend Barbie when they each undergo frightening medical crises. And unfortunately, they aren't the only ones with troubling symptoms: months after the explosion at Shadow Pond that appears to have killed Boris, Hank is still not fully recovered, and his condition is worsening.

Meanwhile, the upcoming nuptials and the arrival of both Owen and Hank's former flame Winnie bring back memories of less happy times, before the Hamptons healed the Lawson brothers and their fractured relationship. As Evan broods over a wrong he may have done Owen years before and Hank assesses his romantic failures, storm clouds move in. With the blizzard closing roads and preventing guests and vendors from making it to the Hamptons, the white wedding of Paige and Evan's dreams is in danger of becoming a snow-covered nightmare.