Night Voices is one creepy poem. 

The first two stanzas seem to be a conversation between a young child and his (the gender isn't clear, but let's assume it is a young boy for the sake of expediency) father near bedtime. The child asks his father, "who is it who whispers in the wood?"

The father, as any parent does, is quick to assure his child. He says, "it is the breeze/As it sighs among the trees." 

But the child is unsure. He is convinced that "there's some one who whispers in the wood." 

The second stanza is the same as the first, replacing whispering in the wood with murmuring in the night.

The third stanza is where things start to change. We (the readers) start to become aware that something is not right. The child asks the father to "let us go,/For the light is burning low." Let us go from where? Why would a child be pleading with his father to let him go? And who is "us"?

In the fourth and final stanza, our whole perception of this poem is drastically changed. For your convenience, here is the whole fourth stanza:

"Father, father, tell me what you're waiting for,
Tell me why your eyes are on the door.
It is dark and it is late,
But you sit so still and straight,
Ever staring, ever smiling, at the door."

Now, the father's actions have replaced the noises in the night as the creepy subject of the poem. The father is not a comforting figure, but stares, "ever smiling, at the door." He is terrifying--the active figure in the horror story. His answers from earlier in the story are under question, and we fear for the future of the children.