Newt's Emerald
Garth Nix2013

After the Newington Emerald is stolen at the height of a conjured storm, eighteen year-old Lady Truthful Newington goes to London to search for the magical heirloom of her house. But as no well-bred young lady can hunt the metropolis for a stolen jewel, she has to disguise herself as a man, and is soon caught up in a dangerous adventure where she must risk her life, her reputation... and her heart.

Balancing twin roles as a young lady coming out in her first season and as an intrepid young man up against an evil sorceress isn’t easy, but Truthful has to manage it. Her father’s life and even the fate of England may depend upon her recovering the Newington Emerald!