This is another of Jean Rollin's 'horror' stories, although this film – after over forty years – comes across as very tame for such an expression, although there is certainly some surrealism.
Set in 1905, Marc (Jean-Maire Lemaire) – the leader of a bunch of criminals who's run off with all of the money following a raid – stumbles upon a castle when making his getaway. The place is only inhabited by two very odd bisexual young women, Elizabeth (Franca Maï)* and Eva (Brigitte Lahaie), who very quickly dominate the situation.
Eva also very quickly dominates the gang in pursuit of Marc, who try to beseige the castle: she fells a potential rapist with a knife blow and mows down the others with a scythe.
But this doesn't mean that Marc can escape with the money: the girls are part of a kind of coven, and even though Eva has fallen for Marc she can't, as one of the anaemic clan, resist her 'natural' desire for killing and blood drinking.
*Franca Maï also went on to direct some very odd films as well as write a number of novels.