Liv is throwing a surprise birthday party for her too-perfect-to-be-true new fiancé, Christoph. And, the party must be flawless so all their friends will know how excited Liv is to be his wife. An amazing party might also help Liv atone for sleeping with her best friend Nate on the night of her engagement. Which meant nothing. Nate is averse to commitments, so he should just add Liv to his long list of women. And he usually could. But, as party time approaches, Nate begins to question his no-strings mantra and decides to make a full court press for Liv's affections.
As Liv is busy party planning and resisting Nate's awkward advances, the rest of their friends head on a collision course through New York City. Prim, proper and newly pregnant Beatrice wants someone to admire her cabinets, while her husband, Paul is freaked out by the baby news. Paul admires Nate's unattached ways and urges his buddy towards Ms. Sexy Hot Boss. Paul may not be able to take advantage of her charms, but he's excited to know that Nate can. It may be torched Earth for Paul, but Nate still has a world of women to conquer.
Across town, Liv's older brother, the non-communicative Sammy, takes his stoner assistant to stakeout Sammy's cheating wife. Where the fault lies in the break up of Sammy's marriage may be unclear, but ignoring the problem, as Sammy tends to do, is not the answer. Meanwhile, drop-out brother Thomas has hired a stripper instead of a bartender and bought piñatas and disco balls to spice up Liv's stuffy soiree. To make matters worse, Christoph's ex, Annie, just showed up to win back her man or to punch him in the face. And, the party is just getting started–with or without the cock cake. When this tangled web of friends finally gathers, some people get lucky, some get even, and some go home in tears.