Lyric discussion by Toronodo 

Never saw the movie. To me, it's a song of encouragement. The brother is telling his sister these things because she is lost in depression, maybe coming off drugs.

Cry, little sister - Thou shall not fall (Cry, but don't go back to drugs or kill yourself)

Come, come to your brother - Thou shall not fly (Come to me, don't fly away on drugs or death)

Unchain me, sister - Thou shall not fear (I am consumed with your misery, get well so I can rest. Don't fear getting well)

Love is with your brother - Thou shall not kill (Be with me, I love you, don't kill yourself)

The verses describe the darkness of the depression.

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