ATTENTION: This thread is for spoilers! Post spoiling screencaps, videos, or information in here! If anyone wants to talk about the ending of the movie, please provide a bold or ALL CAPITAL LETTERS warning before you talk about it. WARNING: It's already been secretly revealed on page 2!
Exactly one week ago, I searched everywhere for the two books released on December 6th for Cinderella III: A Twist In Time. I finally found them both at the bookstore called Borders. With their help, and pictures from the picture book, I have assembled this spoiler-full text that tells the beginning of the movie. One spoiler I will never reveal is the end battle, however. I haven't even peeked at that spoiler myself!
UPDATE: I have seen Cinderella III: A Twist In Time and read both books based on it! So I have finished the plot synopsis and added the pictures from the second half! If you haven't seen the movie, scroll down and read further at your own risk!
So, here's the beginning of the plot! It's been one year since Cinderella tried on the glass slipper and was discovered to be the one the Prince fell in love with at the ball. They decide to go horseback riding for a while. Meanwhile, this is the perfect chance for Cinderella's Fairy Godmother to prepare a surprise anniversary party for the happy couple! The forest is the perfect setting: It's deep and secretive, yet full of beautiful scenery! With a wave of her wand, she creates a flowery gazebo, and with the help of Cinderella's animal friends, she creates a delicious cake.

But Cinderella's stepsisters are not celebrating. Their mother, Lady Tremaine, is making them do all the dirty work Cinderella had to do for the house before she became a princess. Anastasia dreams of being a princess as well. Luckily for her, and unluckily for Cinderella and the Prince, Anastasia sees them in the forest. She follows them to the party. Cinderella and the Prince are very surprised, but it is Anastasia who gets the real surprise when the Fairy Godmother magically changes their riding clothes into the clothes they wore the night they first met!

When the Fairy Godmother drops the wand, Anastasia sees this as her only chance at escaping drudgery like Cinderella did. She grabs it, and runs off to her mother and sister. The Fairy Godmother follows her home, and tries to get her wand back. Anastasia says the magic words, "Bibbidi Bobbidi Boo" to thwart her. But the spell does more than she intended, and turns the old fairy into a statue! Lady Tremaine sees this as not just a second chance to elevate her daughters in status, but also elevate herself to power, and get revenge on Cinderella.

Lady Tremaine casts a spell that turns the wand's white sparkles into a ghastly green mist, and commands time to reverse, gleefully watching her stepdaughter lose her happiness. The spell takes them to a time when they thought they would become happy, the day the Grand Duke arrived to hopefully fit the slipper on one of the girls and take her and her family to the palace. With another spell, Lady Tremaine makes the glass slipper fit Anastasia's foot, so she can be the Prince's bride. Cinderella knew she should be the Prince's bride because she was the one the Prince fell in love with, and she had the other slipper to prove it! But Lady Tremaine broke that one and told Cinderella that she had dreamed up the night with the Prince.

Cinderella knew she hadn't been dreaming, and set off to find the Prince. She believed that if he saw her, he'd know she was the one he had danced with at the ball. Dressed in her work clothes, Cinderella easily fit in with the other palace servants. But Prudence was suspicious of her. With help from Gus and Jaq, Cinderella pretended to be the royal mouse catcher. Prudence saw that they really needed catching!

Meanwhile, Lady Tremaine presented Anastasia before the Prince, showing him that she must be the girl he fell in love with at the ball because the glass slipper fit her. But the slipper's fit wasn't enough for the Prince. He knew he hadn't danced with her at the ball, and told them so. With another spell, Lady Tremaine made sure the slipper's fit was enough for the Prince. He fell in love with Anastasia and asked her to marry him, which she gladly accepted! Cinderella didn't know this, and when she finally found the Prince, he didn't even recognise her!

Cinderella was heartbroken, but Jaq and Gus soon found her and told her evrything they had learned. Now knowing that the Prince did not know her due to magic, Cinderella planned to retrieve the wand from her stepmother. Carefully hiding her face in a maid's disguise, Cinderella entered her stepfamily's room to clean it, while Jaq and Gus tried to get the wand out of the dresser drawer it was kept in. Lady Tremaine is not fooled by Cinderella's disguise, and uncovers her. But Jaq and Gus already have the wand, and run out of the room with it, followed by Cinderella. Lady Tremaine orders the palace guards to capture Cinderella, calling her a thief.

Cinderella gets the wand from Jaq and Gus just as the Prince gets to her, but that is also the moment that the guards get to her, and she is caught. Lady Tremaine takes the wand back and tells the guards to put Cinderella on the next ship leaving the kingdom, to be banished forever. The Prince does not hear this, and hopes that Cinderella will be all right.

But Jaq and Gus tell the prince that everything is not all right. They explain to him that he is under a spell that makes him think he danced at the ball with Anastasia. Then they tell him to rescue the one he really danced with, Cinderella. The King and the Grand Duke think the Prince has gone mad when he gallops out of the castle on his horse right before his wedding to Anastasia.

But the Prince knows he is not mad for going after Cinderella when he sees her on the ship. Touching Cinderella's hand breaks the spell, and he asks for her hand in marriage. Cinderella happily agrees to marry her one true love, and the newly engaged couple returns to the palace. When the King discovers that Lady Tremaine put a spell on his son, he orders the guards to arrest her. But when the guards enter the stepfamily's room, they are nowhere to be found.

(I added the green magic in this picture, for fun

The King doesn't want their disappearence to ruin the happy occasion, and the wedding goes on as planned. But the occasion is ruined for Cinderella when her stepmother enters her dressing room. Lady Tremaine knows that magic cannot work on the Prince's love for Cinderella, but magic can work on Anastasia to make her look like Cinderella! With more use of magic, Cinderella finds herself trapped in a pumpkin coach that takes her far away from the Prince, who will now marry a copy of her.

Cinderella is determined not to let the beautiful dream in her heart die, if she can help it. And she can help it, as she proves by breaking out of the pumpkin and jumping onto the horse that draws it. Cinderella rides the horse to the palace church, where everyone is shocked to see two Cinderellas! Lady Tremaine's plan is ruined, and she is forced to come out of hiding.

But, just like Cinderella, her stepmother is determined not to let her own dream die either, her dream of revenge. With a "Bibbidi Bobbidi Boo", Lady Tremaine creates a swirling vortex of green magic, which starts turning the guards into animals. She prepares to do something to Anastasia, but Cinderella stands in front of her stepsister to block the magic from the wand. This does not trouble Lady Tremaine, who decides to kill two birds with one stone, or get revenge on both of them with one spell.

But the Prince is brave like Cinderella, and stands in front of her and Anastasia. He uses his sword to block the magic, which causes the green sparkles to bounce off of it and hit Lady Tremaine and Drizella, who vanish from the church. The wand is left behind, and Anastasia uses it to return to her true self. She wants someone to love her for who she really is. She is now happy for Cinderella, who can now be happy with her Prince, and they are happy together forever after...again.
