Okay, found the one that got to me -
(Please note: quotes are as best I can remember them. I haven't played the game for about a month now, because my roommate's been pursuing achievements.)
In Mass Effect, select "Colonist" as part of your background. It will turn out that you were one of the few colonists to survive an attack on Mindoir by batarian slavers when you were a child. On your second or third trip to the Citadel, you will be asked to help C-Sec with a young lady on the docks who is basically holding herself hostage. She was captured at Mindoir, and was recently rescued by Alliance forces - but she doesn't seem to believe it.
When you go to help her, don't move toward her too quickly - instead, encourage her to talk about herself, and about what she can remember. She tells a horrifying story, from a child's perspective, of what happened that day, and fragments about her life since. (In her mind, she considers herself to still be that little girl on Mindoir, and considers that everything happened to someone else, because "if it happened to her, it was real. And it can't be real! Can it?"). She tells of watching Daddy "come apart" during the attack, and the slavers taking their captives and "putting the marks in their backs, and the metal in their brains so they can't run away. It makes their heads explode if they run away."
At one point, she fiercely denies crying: "She's not supposed to let the water come from her eyes. The masters beat her if she wastes water."
If you gain her trust, you get the opportunity to offer her the anesthetic that C-Sec wanted you to inject her with, so they could take her to Medical for therapy.
"Will she dream?"
"No dreams - you'll just sleep."
"She'd - I'd like that."
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Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.