"You know, the Chinese say that once you've saved a person's life, you're responsible for it forever."
Scottie says this to Madeleine after he has saved her from drowning. It suggests that he feels responsible for her well-being, and also hints at the fact that he is attracted to her and would like to pursue a romantic connection to her, searching for any excuse to see her again.
"Only one is a wanderer; two together are always going somewhere."
When Scottie suggests that they ought to go for a drive together, Madeleine tries to deflect his advances by suggesting that if they go together, they will not be "wanderers," the label they have each given themselves.
"If I do what you tell me, will you love me?"
Judy, realizing that Scottie is intent on turning her into Madeleine, asks if he will love her if she goes along with it. This quote shows that Judy is willing to do whatever it takes to win Scottie's affection; it also suggests that she can sense the obsessiveness behind Scottie's love, and is unsure about whether they will ever truly be able to love one another.
"One final thing I have to do... and then I'll be free of the past."
After Scottie has realized that Judy is, in fact, Madeleine, but before he has revealed that he knows this, he says this to her. He is planning to take her to the mission where "Madeleine" was killed, so that he can retrace what happened that day and confront Judy about her deception.
"You're gonna be all right now, Madeleine. Don't you see? You've given me something to work on now! I'm gonna take you down there to that mission this afternoon and when you see it, you'll remember when you saw it before, and it'll finish your dream. It will destroy it. I promise you. All right?"
After falling in love with Madeleine, Scottie becomes increasingly invested in curing her of her demons. With this line, he expresses his intention to bring her to the mission building and destroy her delusions once and for all. He thinks that if he can get Madeleine to remember her associations with the mission, he will jolt her out of her insanity.
"Sorry Scottie, that was rotten. He had no right to speak to you like that."
After the hearing following Madeleine's death, Gavin tries to console the guilt-racked Scottie. He insists that Madeleine's death was not Scottie's fault, and suggests that the judge's treatment of him as though he were responsible for the death was unfair.
"I heard that one before too. I remind you of someone you used to be madly in love with, but then she ditched ya for another guy. And you've been carrying the torch ever since. Then you saw me and something clicked."
When Scottie follows her to her hotel room, Judy scolds him for following her, suggesting that he's a creep who's trying to molest her. She is frustrated with his insistence on talking to her, positive that he's just trying to take advantage of her vulnerability.
"You shouldn't keep souvenirs of a killing. You shouldn't have been that sentimental."
Scottie says this at the end of the movie at the mission, when he confronts Judy about the fact that he knows she is the same woman who pretended to be Madeleine. He recognized her necklace, something that Madeleine wore, and berates her for "keeping souvenirs of a killing."
"Oh, Johnnie, Johnnie. Please try. Try, Johnnie. You're not lost. Mother's here...John-O, you don't even know I'm here, do you?"
When Scottie lands himself in the sanatorium, Midge visits him and tries to wake him out of his mania. She refers to herself as "mother" and tries to comfort him, but to no avail.
"I was safe when you found me. There was nothing that you could prove. When I saw you again, I couldn't run away. I loved you so. I walked into danger, let you change me because I loved you and I wanted you. Oh, Scottie, oh Scottie please. You love me. Please keep me safe, please..."
At the top of the bell tower, Judy pleads her case with the furious Scottie, insisting that she stayed with him and didn't tell him the truth because she loved him so much and wanted to try again. She begs him to see her deception as an extension of her love for him.
