Gustave has taken it upon himself to observe Marion and Sanglain following the death of the Princess and DT.   But KT thinks Gustave is in the city of Marquesas for other reasons. 
Are you talking to 
yourself in the mirror?
¿Estás hablando contigo mismo en el espejo?
¿Estás hablando contigo mismo en el espejo?
Você está falando consigo
mesmo no espelho?