So, there is this movie from like the 2010’s, not sure, in which a man moves to an apartment and his next door neighboor is a single mom. They start to get romantical and eventually he figures that there is something wrong with the baby and is related to a witch that wants to kill the baby i guess. I remember this one scene where he wakes up in the middle of the night and there are lights in his room that lead him to discover a secret passage to where the baby is and i think it’s the witch’s lair
There’s an episode of Masters of Horror called Dreams of the Witch House that fits that description. Just a guess!