After placing a keg of dynamite in the buckboard, Lucas accidentally creates a spark leading to an explosion. The flash in particular has affected his eyesight. He is blind and the Doc doesn't hold out much hope that he will recover. With Mark's help, he becomes more adept at getting around but when a gunslinger from his past shows up in North Fork, his life is in real danger as the man is out to kill him.
—garykmcd