Luke snaps and brutally overpowers Vader , severing his father 's mechanical right hand .
Luke keeps his emotions under control until Vader senses that Luke has a sister , and threatens to turn her to the dark side if Luke will not submit .
Luke snaps and brutally overpowers Vader , severing Luke 's father 's mechanical right hand .
Luke keeps his emotions under control until Vader senses that Luke has a sister , and threatens to turn her to the dark side if Luke will not submit .