When Caroline, Adam's eccentric and emotionally toxic sister, shows up unannounced, Hannah offers her a place to stay, despite Adam's protests. Marnie's control-freak tendencies reach full tilt at Hannah's 25th birthday party. Ray settles into his role as manager at the new restaurant, but has a harder time keeping cool around Shoshanna.

Hannah is thrilled to attend an event alongside members of the literary illuminati, until she learns that her eBook deal may be in jeopardy. Later, she tries to help Adam and Caroline work through their anger issues; Jessa makes positive changes; and Ray gives Marnie candid advice.