The Second Floor Mystery plot
"A NEW KIND OF MYSTERY THRILLER!"
Geoffrey West and Marion Ferguson, two American tourists in London, meet at a hotel during breakfast. Both read the personal column in The Times. The next day, West, under the pseudonym Lord Strawberries, places an advertisement asking for her friendship. Ferguson, under the pseudonym Lady Grapefruit, posts a response suggesting that he write a series of five letters to prove that he is worth knowing. West concocts a fantastical story about a murder mystery, based on arguments he heard his upstairs neighbors having. Ferguson's aunt, who dislikes West, suspects him of the murder and contacts Scotland Yard. West's neighbor (the one he mentioned in his letters) is found dead, and the police immediately suspect West and Ferguson of involvement in the murder. The real murderer, hearing that they are the prime suspects, attempts to frame them.