In 1895, Sherlock Holmes seems to have found a worthy rival for the first time in his career. The famous detective is unable to solve a sinister case in the heart of London. Cornered, he must rely on the unexpected help of a young American girl, Amelia, who claims to be his daughter... Amelia, who claims to be his daughter! This unexpected duo must work together to unravel an international conspiracy, solve the mystery behind Amelia's mother's death, and discover whether the young prodigy is truly the legendary Sherlock's daughter.