Monstrous (2022) on Netflix

Plot summary

Laura leaves an abusive ex-husband and drives with her seven-year-old son Cody to a remote house in California in the 1950s. She worries that the man will come after them, and something in the nearby lake visits Cody's room at night. Laura settles into a routine, sending her son to school and doing typing work for a company. Cody is frightened at first, then seems at ease with the visitor, but he stays sad and argues with his mother about going back home, which she always refuses. For his birthday she writes invitations for his classmates and decorates the house with balloons, and no one comes.