Revealing mistake: In the scene where Sgt Howie hits McGregor (who is dressed as Punch) with a candlestick, watch closely and you can see that the blow from Howie is aimed into the padded section on the back of the punch costume, rather than at the back of McGregor's head.
Revealing mistake: Edward Woodward goes to visit Christopher Lee at the big house. In the grounds, a group of pregnant women are performing a pagan ritual involving jumping over a small bonfire. Woodward the Christian puritan looks out of Lee's window and sees this, and exclaims indignantly: "Those young women are NAKED!". In fact, even on a 14-inch TV screen you can see that they are wearing fleshtone body-stockings.
Revealing mistake: Sergeant Howie spots the creepy candle and knocks it to the floor. He falls to the floor himself and extinguishes the flaming thumb, but reaches it through a visible editing job; some frames are missing.
Answer: He was a devout man of faith. They had to test his virtue, to tempt him to break the ten commandments or the seven deadly sins.