Psychological not-quite-mystery story about a babysitter named Pru who cares for a young child born without limbs. Read around 1970s.

[Linda]

I read this book probably in the 1970s when I was a teenager, and it has stuck with me because it was so chilling and unsettling.

I'm hoping the two main details (the babysitter named Pru and the child having been born with no limbs) will narrow down my search and help me find out the name and author of this book, because I would like to read it again now that I'm a mother (and grandmother), to see if it will have a different effect on me.

Thanks for anyone who can point me in the right direction!