Joan has that same voice, the voice that says that this might not be the time, considering she has to go back to Baker Street. But they've been holding back, and now that the dam has burst on being able to be affectionate in public, it's hard not to allow this domino to fall, too.

She answers the happy noise with one of her own, and lets one hand trail down his side to grip the hem of his sweater and tug it upwards.