Such a narrator cannot know more about other characters than what their actions reveal.

The story tells us however that the narrator never knew her last name at all.

Early in the novel, the naive narrator knows little.

The play's narrators all know one another's business thoroughly, yet any closeness among them seems more formal than emotional.

The stories are told as the memories of a black maid the narrator knows.

Shattered, the narrator no longer knows where to turn in what he calls this "land of despair and poetry."

The outer narrator has no direct involvement in the events but knows more than what Sack tells him.

The narrator did not know she was seriously ill.

As my narrator knows well, that might be theoretically interesting, bul no one would read it.