In the summer of 1923, Rose is presented at Buckingham Palace and has her coming out ball at Grantham House.
Finch and Reese try to protect a psychologist who uses unorthodox methods to help patients achieve closure; flashbacks reveal Finch's state of mind after the death of his best friend.
Amid the fallout from the eventful house party, Mary faces a pressing question about her future, while Carson reveals surprisingly intimate details of his former life.
An extravagant house party at the Abbey gives the Crawleys a chance to reconnect with old friends, but some guests prove more welcome than others, and along with the celebrations come deceit and heartache.