Sandoval, Schwartz and Jax vow not to let Lala’s no-show ruin Ariana’s rowdy, NASCAR birthday weekend in Sonoma. Meanwhile, Stassi’s Montauk birthday trip is off to a rocky start when she breaks down in tears over her recent split, and Katie and Kristen fail to find Stassi an eligible Hamptons suitor. Later, Lisa learns troubling news about Lala’s situation, and Scheana feels like an outsider when she doesn’t embrace Stassi’s birthday traditions.