Though it wasn't particularly full of humor, one corner of Lisa's mouth ticked up into her cheek at the other woman's reaction. It wasn't the first time she'd heard a reaction to that question in that manner; most of the time it was just a tell of the person showing it- they find the notion of themselves having children so humorous (or absurd), that they bark out in laughter. Occasionally, it's condescending. Lisa didn't get that impression in this case.
"Ben was kind of a surprise to me, but--" she said, filling the silence as they moved on through the town. Talking about something that was near and dear to her as her son kept her from concentrating on the fact that she swore she heard footsteps right behind them. Every glance back found the sidewalk empty. Like now.
"But we get by. Did you..." She waved a finger back behind them. "Did you hear that?"