Louis Theroux returns to the UK to spend time in specialist psychiatric units which treat mothers experiencing serious mental illness whilst allowing them to live alongside their babies. Immersing himself on the wards, he meets women who have been admitted with a range of serious conditions - including depression, anxiety and psychosis - often triggered by birth or the strains of motherhood. As he follows the patients and their families both in hospital and recovering back at home, Louis explores what lies behind their recent crisis and discovers the immense challenge in caring for two people in the most vulnerable state of their lives.