Sherlock is hard at work trying to track down this person who set Turner Chapman on the path of kidnapping and attempting to murder Ted. When his phone buzzes he expects it to be Watson. When he sees it's Ted Lasso asking where Joan is it pulls him up short. He would have thought she was with him. But finding out that she's not, that he has no idea where she is, he has some idea of what might be going on. He was there when Joan was dealing with Andrew's death. It turned her life upside down, and it took her months to come back to herself again.

Has she told him?

He texts back, in legible vernacular instead of his usual text speak.

She is not. Does the name Andrew ring a bell?