Annie who loves to sing, dance and shop with her friends is forced to spend the summer with her grandmother Nainai and cousin Yong in China. After a construction crew disrupts some ancient statues, a mystical portal opens at dawn and dusk. Nainai, an old warrior, who has kept the evil from the portal at bay, must now train her granddaughter, Annie to fight against the evil that will come.
As Annie begins her intense training for her new role as a Guardian of the Power Masks, her cousin Yong is feeling left out because the male mask was left in the Twilight realm. Then, suddenly Hou Chu, a former Power Mask warrior, who fought alongside Nainai, returns from the Twilight realm, but something is wrong. He has become arrogant and prideful and Yong must challenge him for the mask.
Annie's parents, who are on an archeological expedition in Korea, decide to visit Annie in Singing Rocks. If they knew what Annie was doing, they would take her back to America immediately. But evil forces decide to invade the town just as the parents arrive.
Yong ridicules Annie's American culture because she hangs pop star posters on her walls. But when Yong's favorite action hero Zhang Yu Yi is stranded in Singing Rocks, the tables are turned and Yong begs Annie to help him get an autograph. However, when the portal opens and the action hero must face true danger, will he be a coward or will Yong get to fight with his hero.
Annie receives a letter from her friends back in LA. Anne wants to respond to the letter, but is having a hard time deciding what to write about. She can't let her friends know about her power mask battles or the creatures that come from Twilight, so she tries to write a goblin free letter to her friends.
Yong is deathly afraid of water although he won't admit it. When Dark unleashes a foam-making water nymph into the human world, Yong must overcome his greatest fear and work alongside Annie and Mao to save the town and the lake from being overrun with waves of foam and bubbles.
Annie and Yong get into trouble when they decide to go against Nainai's advice and make decisions for themselves. Yong must now fight with an injured shoulder and Annie tries to keep a 'pet' creature from the Twilight realm. Chaos ensues when Annie's little pet turns into a fire breathing problem. Yong and Annie painfully learn that Nainai's advice is better than they originally thought.
After a slew of freak storms and wilting plants, Annie and Yong discover that the seemingly harmless bird they let go at the portal can transform into a giant creature. The problem gets worse when they discover that the bird has built a nest and laid a giant egg. Annie and Yong must now work to trick the bird back into the portal with its egg.
Yong's new obsession, a videogame named Kung Fu Monster Bash, turns into a big problem when Dark brings the toughest videogame monster into our world. Annie and Young must now battle the videogame monster and stop Dark's evil plan.
Annie goes to visit her parents in Korea, only to find that a Twilight creature had followed her on the sole of her shoe. The creature wreaks havoc as it eats and grows inside a popular Korean store. Annie must figure out a way to defeat this clothes-eating goblin without her mask and without her parents finding out.
Yong chastises Annie about wanting to take a day off from guarding the portal. However, when Yong's best friend invites him to his birthday party and Ori escapes from the Portal at just the wrong time, Yong must learn to balance duty and friendship.
When Yong's favorite martial arts store may close due to lack of help, Yong offers to help the owner. But when the demanding schedule of helping out at the store and guarding the portal takes a toll on Yong, putting Annie in danger, Yong must decide who should In really be the boss.
Through sometimes painful and sometimes humorous situations, Annie and Yong learn the hard way that sometimes, having a little knowledge is so much better than just working or fighting harder.
Nainai teaches Annie and Yong "Never give a sword to a man who cannot dance". Even though he hates dancing, Yong learns to apply dance moves to win the battle and Annie learns to show respect for her opponents.
When a traveling salesman steals the Masks in order to sell them, Annie and Yong must work fast to get them back without their super powers. They learn the thief is highly superstitious so Annie and Yong devise a series of "funny bad luck" events to get the Masks away from the thief and save the Masks for the family.