- The Face Of Boe
- Ood Sigma
- Dalek Caan
- The Grim Reaper
- Captain Jack
- Bad Wolf
- The Drowned Hath
- The Master
Here is the sentence that the phycic woman said:
“It is returning, it is returning through the dark … he will knock four times.”
The sentence does state that the thing which will be knocking the doctor is a he.
Who do you think will be knocking The Doctor four times.