A Casa da Escuridão

Julia, a teacher in a school for the deaf, has a hideosly disformed and deranged twin sister that resides in the local looney bin. She escapes to gate-crash a surprise birthday party for Julia by murdering all the party guests with the help of a giant killer Alsation dog, which gets it's come-uppance when lobotomised by a power drill, in a scene that will offend most animal lovers.