Heather proposes a group trip to celebrate Monica's birthday, causing unresolved tensions between Monica and Lisa to reach a boiling point. Angie leans on Whitney for advice about her marriage woes. Whitney and Justin join Meredith and Seth on their new podcast and open up about the status of their marriage. Heather throws a Pioneer Day-themed lunch to thank her friends for their support, but the day ends with hurt feelings and the upcoming trip hanging in the balance.