In Victorian England, fifteen-year-old Kate's dreams of a life of adventure have, so far, only led her as far as her brother Jack's workshop, where she tests his inventions. But when Jack arranges a trip for Kate to China, she discovers that Jack is not just a hobbyist; his creations are used by the British Secret Service, and now Jack expects Kate to deliver an important item to the brilliant teenage doctor Henry Tattersall. Kate's seemingly simple trip turns into adventure when Tattersall falls ill, and Kate ends up facing off against opium traders in Canton.