Fright

"Fright" (1971) starring Honor Blackman, Susan George, Ian Bannen is a British babysitter in peril movie.

Amanda (George) is a college student who fills in for Helen's (Blackman) regular babysitter who couldn't make it.  Helen and her husband Jim are going out to celebrate some occasion.  They are recent arrivals to the village and live in a large old house.  Helen is somewhat reluctant to go but Amanda does her best to assure her nothing will go wrong.

Of course, being a babysitter horror movie, the boyfriend does visit and they quarrel and she kicks him out.  But who does that face in the window belong to?  Is it the boyfriend or someone more sinister?  We soon find out that it isn't the boyfriend, it's someone from Helen's past who is out to reclaim what is his.  Amanda being the ever vigilant babysitter will do what she can to ensure that she and the child survive the night of fright.