"The Mortal Instruments" is a fantasy series by Cassandra Clare that follows the adventures of a teenage girl named Clary Fray. When she discovers that she is part of a hidden world filled with Shadowhunters, demons, and other supernatural beings, her life changes forever. Clary learns about her unique abilities and her connection to a mysterious past, all while trying to rescue her kidnapped mother. As Clary navigates this new reality, she teams up with Jace Wayland, a skilled Shadowhunter, and her best friend Simon Lewis. Together, they face dangerous foes and uncover secrets that could alter the fate of their world. The series explores themes of love, friendship, and the struggle between good and evil.