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. 
the right side of the 
back of my head throbs.
el lado derecho de la parte de 
atrás de mi cabeza palpita.
siento palpitaciones en la parte derecha trasera de la cabeza.
o lado direito das minhas costas dói.