A few weeks after Twilight becomes a princess, Rarity needs to pick up a shipment of gems she purchased from the Crystal Empire. When she arrives there everything is as normal as she left it when she and her friends defeated King Sombra.

Or so it seemed...

Rarity's on the way to have dinner with Princess Cadence and Prince Shining Armor, when she hears a cry for help. Rarity investigates and finds a pony unconscious on the ground, she helps the pony and gets ready to take the pony to the nearest clinic when she is knocked out.

She was apparently captured for the reasons of a resurrection. The resurrection of King Sombra. Then when things are interrupted things go hectic and one of the members of the cult were captured for interrogation and Rarity's put into a clinic.

She goes back to the area where she was abducted to find something, she found it... and something else that could change everything she knows and loves, forever.