I’m looking for a movie from the 1970s or 1980s where kids take shelter in a house and while sleeping in an attic with the children who live there, overhear that the adults downstairs are going to slit their throats and will find which kids to kill by reaching up and feeling for their sleeping caps. So the kids switch sleeping caps with other kids so the adults kill their own children by mistake. (This story is based on the Hop o my Thumb" fairy tale). I saw it on TV as a kid and have never been able to find it again.
le petit poucet?