Filmed in August 1967 while McGoohan was in America filming Ice Station Zebra. McGoohan only appears in the final scene, although footage from previous episodes and a few voiceover lines are included to give the impression of his presence throughout.

The opening sequence is substantially different. There is a pre-credits teaser, then the standard footage of Number Six resigning and being gassed unconscious. After he wakes up, different music plays and there is no footage of him walking through the Village, running along the beach, or going through the opening exchange with Number Two.

This is the only episode in which they both appear where Patrick McGoohan (Number Six) and Angelo Muscat (The Butler) do not share a scene.

The working title of this episode was "Face Unknown".

This is the only episode in which someone other than Patrick McGoohan portrays Number Six.

This is the only episode of the series in which Number Six touches a woman in an affectionate way, his fiancée, Janet Portland. This is probably because Number Six is portrayed by Nigel Stock for the majority of this episode. Patrick McGoohan objected to doing scenes of this kind. This is probably why intimate scenes were written out of two other episodes which would have featured McGoohan, "The Chimes Of Big Ben" and "Many Happy Returns".

(as Number Six paces his flat)
Number Two: What sort of opinion would you form of that fellow?
The Colonel: Anybody who spends his time doing that must be rather stupid.
Number Two: You couldn't be more wrong. Because he's our most interesting citizen from every point of view... particularly yours.

Number Six: You're still as pompous as ever... Danvers.
Danvers: Where did you get my name?
Number Six: Jonathan Peregrine Danvers. Boorn in Bootle. Took elocution lessons. Came to London, joined the civil service in 1948 as a junior clerk, but moved to this department sometimes later. Mainly at the request of the typing pool. Am I going to see Sir Charles? Well? Or would you prefer me to go on. I'm sure these gentlemen would be most intrigued to hear of your little jaunt to Paris in March 1958. Let me see now, what was her name...

Seltzman: If you really are who you say you ,are you would not have expected me to keep it, would you?
Number Six: No. It's a hopeless situation.
Seltzman: If I had kept it, I would have been very stupid. Silly.
Number Six: You've made your point. I accept it.
Seltzman: But you overlooked one thing. Sentimental people are sometimes stupid. Very stupid.

Seltzman: I will do it... on certain conditions.
Number Two: I'm sure they will be reasonable.
Seltzman: For once, I am dictating.
Number Two: Heil.

In several of the long shots during the scenes that take place in Number Two's office, it is likely not Nigel Stock, Clifford Evans or Hugo Schuster on set.

In several shots during the sequence where Number Six [in the Colonel's body] is driving his Lotus 7 around London, it is clearly Patrick McGoohan, not Nigel Stock in the car. The footage used is taken from the opening credits.

The footage of Number Six (Patrick McGoohan) pacing around his front room, eating toast and drinking tea, is taken from "Once Upon A Time" which, although it was aired after this episode, was actually filmed months before.

Nigel Stock's stunt double has noticeable bushier and grayer hair than the person he's impersonating.