The initial indication of an issue was the blood streaming from the bathroom sink. A few days later, Alexandra Hardie noticed cockroaches scampering out from beneath the bed. Before long, she saw spiders climbing the wall. One day in May 2016, four months after having her first child, Ms. Hardie started yelling that the devil was present in the room. She was so upset that she broke a bottle of red wine on the floor of her apartment in Edinburgh. Her spouse, James, dialed 999, the emergency number in Britain. He restrained his wife, who was considering self-harm, on the floor to stop her from reaching for a kitchen knife. Later that day, Mr. Hardie drove his wife and their baby daughter to a specialized psychiatric facility, where Ms. Hardie would stay for almost six months while a team of psychiatrists, nurses, therapists, and social workers treated her for postpartum psychosis, a mental health condition that can lead to hallucinations and delusions, often focused on the mother’s child. This uncommon condition is believed to result from a mix of genetic factors, lack of sleep, and biological changes following childbirth. However, the center, a facility classified as a mother-and-baby unit, took an approach that no psychiatric hospitals in the U.S. would. It permitted Ms. Hardie, who had had thoughts of wanting to drown her infant, to continue caring for her baby while she underwent treatment, with careful oversight. Mother-and-baby units, such as the one at St. John’s Hospital in Scotland, provide care for pregnant women and new mothers experiencing mental health issues like postpartum psychosis, all while keeping them together with their babies.