Aspiring writer Hannah Horvath is left floundering when her parents stop supporting her financially, flatmate Marnie is beginning to feel suffocated by her long-term boyfriend, and their bohemian friend Jessa has just returned from travelling.

Hannah worries when she realises that Adam might not be practising monogamy; Marnie denies her growing boredom; Shoshanna confesses a secret.

Hannah finds out she has a sexually transmitted disease, and her honourable intentions to inform an ex-boyfriend prompt the dropping of another bombshell. Meanwhile, Marnie is attracted to a cocky artist and Jessa gets a babysitting job.

While Hannah is uncomfortable around her touchy-feely new boss, Shoshanna continues her quest to lose her virginity. Meanwhile, trouble brews when Hannah's diary falls into the wrong hands.

Hannah propositions her boss; Adam has a different idea about his relationship with Hannah; Marnie and Charlie assess their relationship; Jessa is determined to conquer someone she used to date.

Hannah flies to Michigan for her parents' 30th anniversary celebration; Hannah spends time with old friends.