A worried Mrs Hudson approaches Holmes and Watson after a conversation with her niece. The niece's employer, the wife of a French aviation pioneer, is a socialite and when visitors fall ill at her tea parties, Holmes is obliged to investigate. Holmes seeks an invitation to tea and after a fearful crash landing, an injured pilot and a sketchbook full of secrets, Holmes now has the ideal opportunity to investigate further. What they find reminds Watson of his army days in India and after a visit to Kew Gardens, Holmes's suspicions are confirmed. It is necessary to act quickly if a national scandal is to be prevented.