The episode follows the wedding of Princess Cadence and Shining Armor, which is disrupted by the appearance of a changeling queen who has taken the form of Cadence. Twilight Sparkle and her friends discover the truth and go on a quest to find the "Elements of Harmony" to defeat the queen and restore the real Cadence. Love and friendship prevail as the wedding ends in happiness.
1. Princess Celestia invites someone to a wedding.
2. The wedding is for Princess Mi Amor and Shining Armor.
3. Princess Mi Amor received serious threats and Celestia asks for additional protection.
4. Princess Mi Amor is actually a changeling, disguised as Cadence.
5. The real Cadence is found and the changeling queen is defeated.
6. Cadence marries Shining Armor and Twilight helps save the day.
7. Twilight is praised for her efforts and there is a bachelor party.