The captain called and told me that the severed ears Gordon Cushing received were a DNA match for Sarah’s.
Joan’s first appearance in the Pilot
Sherlock: You know, I-I’d quite like to go with you next time. To the cemetery. Obviously, the mistake that you made, it, uh… changed the course of your life. The man seems to have left quite an impression, as well.
Well, you and I have what’s known as companion/client confidentiality, which means that you can introduce me however you like. Friend, coworker, relative, and I’ll play along.