The next day, Princess Celestia, Princess Cadance, Shining Armor, Spike, and Twilight's friends rehearse the wedding in the Canterlot castle. The group soon realize that Twilight is missing only for her to burst into the hall moments later and declare that Cadance is evil, citing her behavior toward the Mane Six, the sudden disappearance of the bridesmaids, and the spell she cast on Shining Armor. After Cadance leaves the room in tears, Shining angrily confronts Twilight's accusations: the spell cast on him was to heal headaches brought on by summoning the protective bubble, the old bridesmaids were only in it to meet royalty, and Shining's guard duties have required Cadance to make all the wedding decisions alone, causing her emotional stress.

Embittered by the hostility towards his bride, Shining revokes Twilight's role as best mare and suggests she not attend the wedding at all. The rest of the group join him as he heads out to check on Cadance, leaving a devastated Twilight alone in the hall. As she laments the loss of her sibling bond and questions her understanding of the situation, she finds Cadance next to her and apologizes, only for the princess to encompass Twilight in a sphere of magic green flame that draws her down into the floor.

In the wedding hall, Princess Celestia is about to pronounce the impostor and a fully entranced Shining Armor husband and wife when Twilight and Cadance burst through the door. After they mention distracting the three bridesmaids with a flower bouquet, Cadance declares that her impostor is a changeling that feeds off of love and can change shape at will. The attendees look on in horror as the fake Cadance transmogrifies into her true form as Queen Chrysalis and reveals her plan to weaken Shining Armor's protective spell over the city so that her minions can break through and take over. As she speaks, a horde of changelings batters away at the magic barrier outside.