With another "Allons!" the speaker is telling us to wake up and get out of the house—whether we built it ourselves or not.
Don't try to protest, now. Our speaker wants us out of the dark. He claims to know everything—and expose it. Man, this guy sure has a strong self-image.
The speaker sees something bad in "you," something "as bad as the rest" (199).
Is he talking to you? Well… do you feel suddenly guilty?
Through people's laughter and dancing and eating, inside dresses and in washed and groomed faces, our speaker sees "a secret silent loathing and despair" (202). Things seem to have taken a dark turn.
There is no husband, wife, or anyone to hear the confession, claims the speaker.
He says that everyone has another self, hiding and sneaking around city streets.
This self has no form and doesn't speak, but apparently it's also "polite and bland" when either out in public—like in a railroad car or on a steamboat—or at home (205). This other self sounds pretty dry and dull.
Sure, it might dress fancy and smile pretty, but the other self is described by the speaker as "death under the breast-bones, hell under the skull-bones" (208)—not good.
Under all the fancy appearances and customary behavior, this other self never talks about… itself.