In The Case of the Woman Who Wasn't Needed (Pt. 1), Mr. Keen, the renowned tracer of lost persons, is approached by Henry Frank, a distraught husband whose wife, Ethel, has mysteriously vanished. Henry, a 55-year-old man, is at a loss, insisting that there is no reason for Ethel to leave him after 28 years of a loving marriage. He hesitates to report her missing to the police, believing it to be too preposterous to be true. However, after speaking to his sister, he realizes that Ethel has not gone to visit her, prompting him to seek Mr. Keen's expertise.