A lawyer friend becomes drawn into a mysterious series of assaults and a locked-room-like moral puzzle after a witness describes a brutish figure who inspires fear. The investigation links the coarse intruder to a respected doctor whose secret experiments allow the emergence of a smaller, more violent alter ego. The narrative unfolds through legal inquiry, witness accounts, a scientist's chilling testimony, and the doctor's own written confession, revealing themes of duality, repression, and the ethical risks of scientific curiosity.