Downton Abbey can bring back Gwen, the former maid and current “Mrs. Harding,” wife to Hillcroft College treasurer John Harding, and have her tell the story of the young feminist Lady Sybil helping her get her first job, but don’t for a second think this counts as bringing back Sybil as a ghost.
If this is your idea of a ghost, then you’ve got some thinking to do. In some people’s minds, you can feel the presence of a ghost in a conversation at the dining room table, hear it in people’s voices and “see” the long-dead person who's being discussed in the eyes of everyone affected by her. My idea is that when a ghost enters a room, you actually lay eyes on the physical specimen, preferably in a flattering costume.
For example, the next time Robert winces from another episode of whatever it is that is causing the stabbing pain in his gut and is destined to kill him, have it be when he’s alone in the drawing room so he doesn’t get to say to Lady Grantham, “I can’t drink Bourbon any longer, unless, of course, it’s Knob Creek.” Instead, have him keel over and appear to actually be dying. And then, as it looks like some essential internal pipe has blown and he’s hemorrhaging bigtime, have Sybil appear in her nurse’s garb to staunch the wound with heavy pressure applied to the abdomen, whilst kicking over a couple of tables and chairs to awaken the house.
Tom and Mary are first to arrive, and it’s no coincidence that they are together. They don’t see Sybil and neither does Robert, but he sure feels her and is doubled over from the pressure she’s applying to his gut, which is actually saving the man’s life.
Doctor Clarkson is quickly summoned, and during the wait Lady Sybil comes to see in the guilty faces of Tom and Mary that…well…”finally you two!” (She doesn’t care! Do you think she was going to wait all those years in heaven for Tom to get old and flabby and die?)
Needless to say, there should be evidence of more such scenes to come "On the next episode of Downtown Abbey."