The Master kidnaps a mother and her young daughter (maybe 6 years old) to be his new wives. His other wives say she will grow up eventually, but it's still very creepy that he's taking a child as his bride.
Sexual assault isn't shown onscreen but it's strongly implied. The Master kidnaps and hypnotizes women to be his wives, and it's said that his assistant Torgo "does things" to them while they can't move.
Creepy rape undertones with the master's brainwashed slaves. Also a bad movie in general. I recommend watching the MST3K version for maximum enjoyment.