Midnight Mass Explained
8. Mildred Sees A Face
One of the handful of jump scares used in Midnight Mass sees Sarah (Annabeth Gish) startled by her elderly mother Mildred's (Alex Essoe) cry of terror during the night.
Mildred claims that she saw the face of her late husband staring at her through the window. Sarah dismisses the outburst as a sign of her mother's detreating condition. However, despite not being shown onscreen, Mildred definitely saw something.
A shadowy figure with glowing eyes has been glimpsed by other characters previously and will be seen by others, too. It's likely that Mildred saw the vampire lurking in the night for its next meal.
However, it's also possible that Mildred saw Father Paul, who's actually the elderly John Pruitt after having his youth restored by a vampire while on a trip to Damascus.
Pruitt and Mildred were once romantically involved years ago, with Sarah being the result of their forbidden love. Mildred even recognises him as John when they first meet, though this is likewise dismissed as part of her dementia.
Mildred may have saw John gazing into the home of the family he could've had and mistook him as her late husband.
However, the former scenario is the most likely here.