Instinct is the third episode of the second season of Two Sentence Horror Stories, which aired on January 19, 2021.
Sometimes you just have to grin and bear it.
I saw the corpse’s smile, and knew she’d done the same.
Anika is a horror writer working side jobs until she can publish her first novel. While sitting outside, her hyperactive imagination treats her to a hallucination of a woman being brutally murdered in a hallway, only for the illusion to dissipate shortly after. After talking briefly with her sister, she heads out to Patrick's house to paint his wall for him for some side cash.
While Patrick welcomes her inside and invites her to help herself to anything she needs while working, he exhibits a strange vibe, and even takes a picture of Anika without her consent. After a moment he realizes his mistake and apologizes, claiming to have been taking a picture of the wall for a before-and-after comparison, promising not to have her in the "after" picture. At length, he departs and leaves her to work.
Looking for certain painting supplies, Anika discovers strange masks and needles in Patrick's house, which he notices, feeling his privacy to be invaded. Even so, he clarifies that his wife Holly had cancer in her later years, requiring the supplies. Still unnerved, Anika returns to paint the wall, although she notices a piece of jewelry and a broken tool, prompting her imagination to conjure up an illusion of Patrick murdering Holly by choking her to death with the broken stool.
The hallucination of Holly becomes self-aware and soon takes on a life of its own in Anika's eyes, taunting her. She suggests ways in which Patrick murdered her by occasionally reforming in the position of suggested death, e.g. by reforming on the floor with a knife in her stomach to suggest murder with a knife. After this, Holly continues, urging Anika to spy on Patrick to discover whatever secret he appears to have, but Anika starts ignoring the hallucination by focusing on painting the wall.
The hallucination keeps pestering Anika until Patrick interrupts, offering her some lunch and a drink. Suspiciously, he's aware that she's a vegetarian despite her never telling him this, but he assures her that she mentioned it when she arrived. However, she notices a gun nearby, so she asks for sparkling water while she investigates it. He rattles off a litany of options until he drops a wine glass and gets blood everywhere, asking for her help to clean things up. He returns to making lunch while she cleans, but her paranoia has turned up to 11, and eventually she can't take it anymore, deciding to leave with the job unfinished.
Patrick is naturally displeased by this lack of professionalism, and begins to protest, but she pepper sprays him and tries to leave, running straight into cops that she had called. They immediately finger her as the assailant, so she follows her instincts and goes to a very specific painting, suspecting evidence behind it, but finds nothing. She's about to be arrested when Patrick saves her, assuring the cops that no charges would be pressed; however, just after the cops leave, Patrick tells her she should have followed her instincts.
Looking down, on the other side of the picture frame, are several pictures of his murdered wife. He moves in to kill her, but she manages to stab him to death first.