Enola Holmes wakes up on her 14th birthday to find her mother missing. Her two older brothers, Sherlock and Mycroft, find clues that suggest Mrs. Holmes has run off and plan to send Enola to boarding school. Enola deciphers clues left for her by her mother and decides to run away herself. On her journey, she gets involved in another mystery involving the missing Marquess of Basilwether, a young boy who’s parents fear has been kidnapped.