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. 
After a thorough investigation 
of places he went,
Luego de una minuciosa investigación 
de los lugares a donde fue,
Tras una minuciosa investigación 
de los lugares por los que pasó,
Após investigar alguns
lugares que ele foi,