Basically, this is a by-the-book episode: there's a secret formula and some bad guys want to steal it. But this time their method is different: they employ the skills of a master of the black arts to control and summon those who have the information they desire. So we simply remove all the usual James Bond-y elements, and replace them with clichés from the Hammer Horror studio. There's all sorts of nonsense about spells and charms, and several wasted minutes where robed extras gyrate around, waving their arms as if on some sort of demonic teen dance show. Fortunately, this appears to be the guilty screenwriter's only contribution to the Avengers canon.
Review of Warlock
