It was a simple motivation. I lusted after two young women, so I kidnapped them, held them captive, and fucked them when I wanted. I hoped they would eventually look forward to when I came in to fuck them.
Two boys finally have enough of their sister's teasing and annoying habits. They use their practiced skills to maliciously reduce her to another sex slave.
The story is set largely in the late 1960s. Two young lovers wrestle with the age-old problems of romance and postage. That reminds me, I should reread The Crying of Lot 49.