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. 
that they would reveal all 
their secrets so easily.
como para revelar sus 
secretos tan fácilmente.
como para revelar sus secretos a la primera de cambio.
que revelariam seus
segredos tão facilmente.