Tyrion gets himself some wine while Cersei calls him odd. I'm not saying she's wrong. She's heard that Joffrey wants to go do some fighting himself. Tyrion praises this as an admirable instinct in a young king. Cersei says he's only a boy, but Tyrion points out that there are plenty of boys fighting his war for him. And anyway, Joffrey is seventeen, which was an age at which "Uncle" Jaime was killing people with wild abandon. This is a world where if you haven't killed anybody by seventeen, there's something wrong with you. Cersei says Joffrey's place is not on the battlefield, presumably because she knows he'd get killed instantly. Tyrion says his place isn't on the throne either, presumably because he's going to get all of them killed eventually. Cersei changes the subject and asks Tyrion if he knows why Varys is so dangerous. Tyrion's first guess is that it's because Varys knows everything. No, it's "Because he doesn't have a cock." Tyrion points out that Cersei doesn't either. That may have been her point. She tells Tyrion, "That little worm between your legs does half your thinking." He mildly protests that it isn't that little. Then he notices that Cersei is happy, which makes Tyrion suspicious. Something is clearly going on. She tells him that she has his "little whore." By way of explaining her anger, she says, "You stole my only daughter. You plot to have Joffrey killed." Yeah, yeah. Get used to it, sister.
Tyrion asks, "Where did you find her?" He's not giving anything away. Cersei says she knew her from the Lannister Lion Necklace, which she characterizes as remarkably sloppy work. Tyrion tells her you don't buy a whore -- you only rent them. I believe that is the usual arrangement, yes. But she knows he likes this one very much. She asks, "Could it be love?" Cersei says the whore will be fine, unless Joffrey is hurt. And if he dies, "there isn't a man alive who could devise a more painful death for your little cunt." Tyrion asks how he knows she's alive. Cersei has her brought in. It's not Shae, which I have to think Tyrion suspected, since he carefully avoided using her name. In fact, it's Ros, the most popular prostitute in all of Westeros! I bet she's sorry she ever left the Winterfell-adjacent brothel now. Tyrion walks up to her and apologizes that they hurt her. He tells her she must be brave and that he promises to free her. Instead of saying something like "I'm not your lover!" she just says, "Don't forget me." Tyrion: "Never." She's hustled out. Cersei smirks. Tyrion tells her he will hurt her for this. The day will come when she thinks she's safe and happy and then he'll wreak a terrible vengeance, blah blah blah. They don't mention the part about Lannisters paying their debts, because that has less oomph when one Lannister says it to another. Cersei tells him to get out and she smiles a little.