Department S S01E18 - The Ghost of Mary Burnham

When John Burnham and his wife Mary are leaving their house, Mary is gunned down by a hidden assassin and then dies at the hospital. Soon after, however, her husband starts seeing her and hearing her voice again... Sir Curtis wants Stewart and Annabelle to keep the near-the-edge Burnham under 24/7 surveillance in order to 'protect' him, yet without telling them what from, or why he is 'an important man to the world'.

It doesn't take them long to realize that Burnham is really on the brink of a nervous breakdown - but how do you protect a man from a 'ghost'? Yet when Stewart and Annabelle witness a 'phone call' from the deceased wife, they become convinced someone is purposely trying to drive Burnham over the edge. When they find that the phone is bugged, they also discover there are more people keeping tabs on Burnham - but who and, above all, why?