It's the Great Masquerade, Naomi Clark 90210 : Season 4 Episode 7

Naomi has to work with her arch-nemesis Holly to throw a campus costume party, leading to unfortunate consequences. Navid's plan to bring down his Uncle Amal is threatened, while Silver discovers that political candidate Marissa Harris-Young is not who she seems. Meanwhile, Adrianna handcuffs herself to Dixon in an attempt to get him to stay sober and Annie must decide if she wants to give Patrick another chance.