THE MAD ROOM (1969)
Directed by Bernard Girard
Starring Stella Stevens and Shelley Winters
Hard-to-find horror film about an attempt to cover up a murder in an eccentric household.
Stevens is set to marry Winters' stepson, when she learns that her own teen brother and sister are being released from a mental institution, where they were put after allegedly killing their parents. Winters agrees to take care of the two, but is hacked to death after learning the truth about them.
One very memorable scene has a dog carrying around a severed human hand—pretty heavy duty stuff in the late 1960s.
The ending (when the truth about the whole situation is finally revealed) is especially chilling in this unjustly forgotten film, tragically unavailable on video.