In the magical dimension of Coventry, the royal witch Miranda gives birth to identical twin daughters on Halloween night, Emma Adele Galvin on Halloween night. The sisters are named Apolla and Artemis after the Olympian twins, the gods of the Sun and Moon, respectively; in accordance with their namesakes, Apolla wears an amulet in the shape of the Sun and Artemis wears an amulet in the shape of the Moon. Their father Aron DuBaer, a powerful warlock, transfers the entirety of his magical powers to protect them from an evil entity known as the Darkness and is killed in the process. Karsh and Ileana WarBurton, a magical couple and friends of the family, assume the task of protecting the twins and flee to a non-magical dimension known as Earth to give them up for adoption. Apolla is adopted by a wealthy couple who name her Camryn Elizabeth Barnes, while Artemis is adopted by a single mother and is named Alexandra "Alex" Nicole Fielding. Alex grows up to be a night owl and stays up until the moon sets, writing about the chronicles of magical twin sisters, unaware that her stories are true. She shares a single bedroom with her close friend Lucinda, after her mother Toni Meyerhoff passes away a few months prior to her 21st birthday. Meanwhile, Camryn is a passionate artist and a lark, who wakes up at sunrise to sketch realistic pictures; unbeknownst to her, the images she creates are of Miranda and her homeland Coventry.
On the twins' 21st birthday, Camryn and her best friend Beth decide to shop, while Alex tries to look for a job. After Karsh and Ileana manipulate Alex into entering the store where Camryn is trying on clothes, the sisters encounter each other for the first time since their infancy. Although Camryn is overjoyed to discover Alex, the latter flees the store, prompting the former to grasp her hand, causing a burst of energy. As their magic is released, they discover that they share a sisterly bond and attempt to understand each other. Karsh and Ileana reveal themselves to the twins and inform them about their magical background, after which Alex realizes that her stories about Coventry are true. According to an old prophecy, the sisters are the only ones capable of vanquishing the Darkness and restoring Coventry. As she has the gift of knowledge, Alex refuses to help fulfill the prophecy because her stories end with death. Camryn manages to convince Alex to stay, assuring her that they are unstoppable together, and the two practice their magical powers as they bond.
In the meantime, Miranda senses that her daughters are alive and informs their uncle Thantos, whom she married after Aron's death. The Darkness arrives at Alex's apartment, but the sisters manage to transport themselves to Coventry, and the experience overwhelms Camryn. Despite her sister's pleas, she decides that she does not want to venture further into their destiny and leaves for her birthday party on Earth. Alex, determined to help Coventry without her sister, reunites with Miranda and meets Thantos, who informs her that if Camryn is alone, she is powerless against the Darkness. At her party, Camryn discovers that she used to draw a face in the Darkness and learns from it that Thantos is responsible for the Darkness, and she escapes to Coventry after Karsh and Ileana sacrifice themselves to help her. As she reveals their uncle's crimes to Miranda and Alex, Thantos arrives and admits to killing his brother Aron in an attempt to acquire wealth and power. Thantos then captures Miranda and goes on a rampage around the castle. The twins combine their magic of light and love to vanquish him and restore Coventry, simultaneously reviving their mother Miranda, Karsh, and Ileana. They then celebrate their birthday on Earth, alongside Alex and Camryn's adoptive parents, David and Emily.
