Curate, connect, and discover
Frankie goes nonverbal a lot, especially once he starts dating May because he doesn't have to mask nearly as much/at all, so May gets used to it. They're prepared to order Frankie's food at a restaurant for him, to tell Lance that "it's not a good day for singing", to declare that they're leaving a store because it's all just too much so Frankie doesn't have to. They don't even have to think twice about it, they just make sure Frankie is as comfortable as possible and make sure he knows how much they love him.
May gets used to it, but neither of them expect the day that May just suddenly can't talk and they can't explain why and is this what it's like for Frankie? They try to push through but can't, and when they can't support himself anymore, that's when Frankie steps up. He orders May's food and he tells Juliet "today's not a good day for singing" and he declares that they're leaving a store because it's all too much so that May doesn't have to.
And all May can think is how grateful they are to have such a loving partner and how they wish they could tell Frankie that but they just. can't. It makes them tear up in frustration. Frankie just looks over and smiles sadly. He squeezes their hand and tells them, "I know." And that makes May lose it, so they just stay at home the rest of the day and Frankie makes sure they're completely comfortable and they just spend the rest of the day snuggled up together, completely silent, but hearing each other better than ever before.