WHAT? First of all, that is not the kind of thing you shout at someone on the street, unless you have no class, and until this season, Carla had some. Second, if that's true, then she really had no call to get all shirty with Peter when he initially asked her whether there was even a chance that he might not be Reese's father, besides which, she has gotten pretty far using Benton by keeping him under this delusion, so that, to all intents and purposes (as far as I'm concerned), he might as well be his father, even if biology doesn't bear it out; it's not like the biological guy has been sneaking in visits on the side, unless Roger is the biological father, in which case this whole custody battle would have never gotten as far as it has. And if it isn't true, this is a pretty shitty gambit for her to pull out of desperation. Either way, this really doesn't make Carla look too good, and while she was never set up as a saint, she was never...um...evil before, and I'm really flummoxed as to why the producers would resort to this plotline just to make Benton look good -- and sympathetic -- by comparison.
Anyway, Carla drops this bombshell, and Benton says, "What?!" Carla seems to realize she screwed up royally, because she starts talking fast: "He may not be yours. There was somebody else. It was just casual. And then there was you." When Benton doesn't respond to any of this, her tone completely changes from contrite fallen woman to shrieking, defensive harpy: "I did it for Reese. He needed a father and Roger can be that." Benton finally breaks the spell, sticks his finger in her face, and growls, "Reese is my son, Carla!" She looks taken aback at the vehemence of his reaction. He picks up his bag and quietly says, again, "Reese is my son." I'm convinced.