Z (2019)

Kevin and Beth Parson's son Joshua “Josh” develops an imaginary friend called Z. Initially, his parents dismiss Z as a harmless phase in Josh's childhood but Josh begins exhibiting uncharacteristically disruptive behavior at school which leads to his suspension. At an indoor amusement park, Beth observes a monster-like creature chasing Josh inside a slide, before chasing him and finding Josh seemingly unharmed.

Josh's suspension leads to their ostracization from other parents. At a playdate, Josh throws fellow classmate Daniel down the stairs, heavily injuring him. While sorting through old items in her house, Beth replays a childhood tape and shockingly learns that she also had an imaginary friend named Z. Beth puts Josh on medication behind Kevin's back, much to his dismay after he finds out. That night, a keyboard toy commands Beth to "imagine Z". Following this instruction, she summons Z and learns it is real.

Beth visits Josh's psychiatrist Dr. Seager who reveals that Beth was once a patient of his. Dr. Seager theorizes that Z is using Josh to connect with Beth after a young Beth made a promise to marry and start a family with Z. Meanwhile at home, Z kills Kevin, sets the house on fire and kidnaps Josh. Beth successfully pleads Z to release Josh and takes him to her sister to take care of him. Beth returns to her childhood home and summons Z, fulfilling its wish of marrying her and living together. Z begins terrorizing Beth in their "marriage" before leaving the house to look for Josh. Z lures Josh onto the train tracks as a train is approaching him.

Dr. Seager calls the police on Beth and informs her that because she created Z, she can also end Z. Beth hangs herself almost to the point of death before police barge in to save her. Josh is saved, and returns to live with Jenna and a heavily paralyzed Beth.