There are lots of people in happy marriages who turn out to have terrible secrets or to have done some awful deed in the past that must be paid for in the present. In Doyle’s stories, those are the ghosts you need to worry about.
Mark Gatiss, 2012, x
One can read this in connection with the special but it makes an awful lot of sense for series 3. And probably series 4 as well.
(via gosherlocked)