She began to devote herself passionately to the piano, which had formerly stood forgotten in the corner.

There, at the piano, began the adventure.
"The MAN appeared." Posdnicheff seemed embarrassed, and twice again there escaped him that nasal sound of which I spoke above.

I thought that it gave him pain to refer to the MAN, and to remember him.

He made an effort, as if to break down the obstacle that embarrassed him, and continued with determination.
"He was a bad man in my eyes, and not because he has played such an important role in my life, but because he was really such.

For the rest, from the fact that he was bad, we must conclude that he was irresponsible.