I was shocked to read yesterday that both commenter LogopolisMike and comics curmudgeon Josh Fruhlinger both thought Martin and Gabby were in the apartment to get Bobbie's gun. You guys, that's a really thoughtful idea and all, but I think that gun has already, quietly, been whisked away. It's fun to think that little details, like a gun that never went off, could come back into play at any moment, but Margo has a friend in the police department! Doesn't that give you all the explanation you need?? Unless that errand just totally slipped Margo's mind and the gun's been sitting untouched in her sock drawer this entire time. Which is.... very possible. Okay, comment retracted.
Nevertheless, it looks like their taking pictures to use as evidence, either for I Dressed in the Dark or maybe I Decorated My Apartment in the Dark. Your candles and stationary doesn't have to match your walls, ladies!