Now Sara gets to cross-examine Brian. And by cross-examine we mean… well, that's exactly what we mean. No euphemism here; she just asks him questions.
In the middle of asking him questions, all of a sudden, something clicks within Sara—she realizes "if we lose Kate today, we will have had her for sixteen years, and no one can take that away" (8.2.24).
She's ready to live and let live (or die, in this case) and she just wants her husband back.
Brian moves back into the house that night, and they tuck Anna into bed.
Sara admits that Anna reminds her of herself.
And back in the bedroom, well… now it's time for Sara to cross-examine Brian, if you catch our drift.