Applejack went deaf, and all her friends and family have left her. Her reminiscence is all she has left, and a strange blue unicorn can help her do just that.
Twilight Sparkle died three years ago. Pinkie Pie has been on the Most Wanted list for over a year. Spike took his own life last month. Rainbow Dash is in an insane asylum. Rarity and Sweetie Belle live on the streets. Fluttershy moved to the far reaches of the Crystal Empire. Scootaloo was in a scooter accedent that left her hospitalized and bound to a wheelchair for life. Big Macintosh had a plowing acident that left him without his hind legs just last week.
Applebloom and Granny Smith died in a barn explosion that left Applejack deaf, and her reminiscence is all she has left.