Agents working along the Corinthia Pipeline are disappearing one after another. Steed locates the last who convinces Charles, their superior, that Steed is a traitor. So Steed is sent to an interrogation facility, run by a beatnik known as "The Wringer". Cathy, meanwhile, discovers that Steed's superiors have been negligent in their management of the facility, and it appears that it's now being used for diabolical purposes.
In my opinion, this is one of the best of the Cathy episodes, if not one of the series' all-time best. It features a well-written script and outstanding guest peformances including Terenece Lodge who was equally as great in Man with Two Shadows.
As The Wringer and Bethune re-enter their control room after putting Steed in his cell, Bethune begins speaking before he reaches the mike making his first few words almost inaudible.
After visiting Steed in his cell, Cathy has to wait patiently while the guard tries to open an uncooperative cell door.
The air shaft which Steed and Cathy escape through, wobbles quite a bit as they are crawling along.