Thinking about when Langdon sees Mel for the first time, during introductions, and is actively listening and watching.
Imagine, like, your marriage is struggling, and a new coworker who is like your nerdy fantasy (and seems to be a really nice person) comes to you specifically for help with a case. And she is so interesting that you can't look away when she talks, and also you want to communicate that you respect her so undivided attention it is but, hey, why did your demeanor change entirely? Why does she make you want to be kinder? Why did your heart rate kick up just a little bit?
And then you haven't had a crush in a long time so you forgot how fun it can be (or what it even is; maybe you think you're just enthused at work). You seek her out. You try to make her laugh. You volunteer her to do tasks with you that you suspect you'll both enjoy. You see her smiling at her phone so you try to get a peek. (Is she talking to someone? Are they flirting?)
Meanwhile, you're also anxious that your new dog, that was supposed to be like a fun, cool band-aid for the household, may have agitated the stress in your marriage? And you won't know until you go home so you just have to stew?
And this pretty, impressive woman, who is good at her job, is coming to you for guidance. She looks at you with bright eyes and a big smile.
Are those butterflies in your stomach, or is it just more anxiety?