"Do you want me to beg?"
"Yes."
"Please."
She never begs for anything again. Not to him, and very likely not for anyone else either. He doesn't expect her to, really. And so he is understandably surprised when he receives that text. He opens the message, expecting to find an invitation to dinner, per usual. Instead he finds a plea, and a confirmation that she knows everything. He doesn't even notice his lip quivering, but John does. He pays it no attention when the doctor points it out.
The words themselves are not something one would usually consider to be anything but a declaration. But he knows better. He knows she has seen the video of what he said to Molly during Eurus' cruel games. He knows why Eurus sent the video to her. He knows it is difficult to hurt her and yet he has still done it. He knows she is begging, hoping for an explanation as he looks at the words on the screen that, thought sent by her, were not her words. He knows he is witnessing Irene Adler at her weakest in the text.
"I love you," she says, and he worries, not because she doesn't but because she would never say it.
Notes: Hopefully it wasn't too vague!