In Brian De Palma’s Sisters, the titular siblings are French-Canadian Siamese twins surgically separated as adults. Danielle is gentle and lovely, and Dominique gloomy and anguished. This dynamic is complicated by the fact that the former needs the latter to develop her persona. Without Dominique, Danielle has no identity. To weave the fiction of her socially acceptable behavior, she must have Dominique bear the burden of her most disturbing desires. Yet the film, oddly enough, is not about Danielle or Dominique, but about the journalist Grace Collier. As Dominique recedes into the background, Danielle and Grace become the main antagonistic pair, a transition that culminates in an intense climax, a hypnosis dream, that imagines them as conjoined twins. As we learn, Dominique has been dead from the outset, and Danielle has transformed into her in moments of sexual and emotional excitement.
Read More about Inconstant selves in Brian De Palma’s ‘Sisters’