When Sherlock was addled by his addiction to drugs, his father checked him into a rehab. After six months, he allowed his son to inhabit one of his properties but the gesture didn't come without strings. In conversations with Watson, Sherlock has mentioned that if he ever relapsed or ditched his sober companion, his father has made it clear that he would throw the detective out into the street.
"Morland is the one who cleaned Sherlock up the first time," said Doherty. "The brilliant and functional Sherlock Holmes that we've enjoyed over the last three years, that's Morland's work. With Sherlock relapsing, it seemed appropriate to bring dad back into the equation."
Noble summarized the situation with one of his character's lines: "You made a mess. I'm here to fix it."
While the characters are clearly hoping to address Sherlock's problems, we'll have to see what—if anything—Morland is hoping to fix. But that's always been a central part of Elementary.
"One of the themes that we’ve always tried to explore on the show is this idea of fixing yourself," said Doherty. "We're a show about broken people in repair... We manage to have fun in spite of the fact that the people on our show have real problems and they’re trying to address them in the best ways that they can. That particular theme resonates with people it makes all of us feel good."