The speaker is alone and starts to feel something that isn't there: long, bony fingers touching them. Right away, they talk themselves out of it. "This is just my imagination." But the reassurance doesn't help, because the line that follows is "I'm still lonely." Even if the fingers aren't real, the loneliness behind them is.
The second stanza moves from the body to the mind. The speaker describes "the madness / of being alone," as if isolation itself is wearing them down. The last two lines are the quietest and the saddest: the "voice inside" is "losing every tone," so even the speaker's inner voice is going flat and empty. The mood is eerie but mostly sorrowful. The short, plain lines and simple rhymes make it feel like a whisper, and the poem suggests that loneliness can be frightening not just because nobody is there, but because of what the mind begins to invent and lose.