Secrets which other men did not carry in their breasts

It bears repeating from my last post: we are introduced to the Baron Palaméde de Charlus, born to the Faubourg Saint-Germain, as haughty, eccentric, in his 40s, who blatantly stared at M. 

"[T]he circumspect and unceasingly restless expression of those eyes, with all the signs of exhaustion which the heavy pouches beneath them stamped upon his face, however carefully he might compose and regulate it, made one think of some incognito, some disguise assumed by a powerful man in danger, or merely by a dangerous—but tragic—individual. I should have liked to divine what was this secret which other men did not carry in their breasts and which had already made M. de Charlus stare seem to me so enigmatic when I had seen him that morning outside the Casino."