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 skulduggery and heartache.

Amid the fallout from the eventful house party, Mary faces a pressing question about her future. Carson reveals surprisingly intimate details of his former life, and a trip to the bright lights of London sees Rose put the reputation of the Crawleys in jeopardy.