Therapy is not simply a domain or form of medical practice, but also a metaphor for and a performance of medicine, of its functions and status, of its distinctive mode of action upon the world. This article examines medical treatment or therapy (in Russian lechenie), as concept and practice, in what came to be known in Russia as defectology (defektologiia) - the discipline and occupation concerned with the study and care of children with developmental pathologies, disabilities and special needs. Defectology formed an impure, occupationally ambiguous, therapeutic field, which emerged between different types of expertise in the niche populated by children considered 'difficult to cure', 'difficult to teach', and 'difficult to discipline'. The article follows the multiple genealogy of defectological therapeutics in the medical, pedagogical and juridical domains, across the late tsarist and early Soviet eras. It argues that the distinctiveness of defectological therapeutics emerged from the tensions between its biomedical, sociopedagogical and moral-juridical framings, resulting in ambiguous hybrid forms, in which medical treatment strategically interlaced with education or upbringing, on the one hand, and moral correction, on the other.