The Anniversary

When Sherlock tells her to clear her calendar on December 16th, she has no idea what he's up to. And he isn't exactly being forthcoming with the details. Every time she tries to trick him into revealing something about the plan, he is (of course) two steps ahead of her, easily sidestepping the question or only hinting at the answer. So when the morning finally comes, she has no idea what to expect. With Sherlock there is no way to prepare for or guess at what's to come, so her plan is just to go with the flow, let him lead the way. He likes to do it anyway.

He's already up when she awakens and she pulls on her robe before padding out into the sitting room to find out what he's up to. A fire is going, which is good because the rest of the flat is chilly.