The lying detective

John blames Sherlock for Mary's death and refuses to see him. Lost without his friend, Sherlock becomes paranoid and declares that Culverton Smith, a powerful magnate, is a serial killer. Why ? Because he met his daughter, who claims the Smith Company created a drug that can erase a short period of memories, and that her father confessed his crimes before having her taking this drug. Are Sherlock and the young woman both storytellers ?