Contains spoilers for this episode.
Marie signs her daughter Sara up for Arkangel after briefly losing her in a playground. The implant lets Marie track her location, monitor her health and watch through her eyes. It can also obscure distressing sights and sounds. That protection creates unfamiliar dangers: Sara cannot properly see her grandfather's collapse, and later experiments with hurting herself because even the sight of blood is hidden from her.
After professional advice, Marie puts the tablet away and allows Sara to grow up without the filter. Years later, a night out that does not match Sara's story draws her back to the controls. She secretly watches Sara having sex with Trick and later taking cocaine. Instead of speaking openly with her daughter, Marie threatens Trick into ending the relationship and mixes medication into Sara's drink without telling her.
Sara becomes ill at school and learns that she had been pregnant. Finding the packaging and the hidden tablet reveals how far her mother has interfered. Their confrontation becomes violent when Sara strikes Marie with the device. The filter blurs the injuries as she hits her, preventing Sara from fully seeing what she is doing until the tablet breaks. She flees and accepts a lift out of town. Marie wakes and calls for her daughter, now unable to locate the child she tried to watch so closely.