Season 4 of “American Horror Story” isn’t even halfway over, but fans of the hit FX miniseries are already speculating about Season 5. Following co-creator Ryan Murphy’s confirmation that a “big Season 5 clue” has already been revealed, viewers are in full Nancy Drew mode.

During an interview with Entertainment Weekly, Murphy said a top hat is a hint about the plot of Season 5.

“It’s an arcane clue,” Murphy said of a scene where Maggie (Emma Roberts) is handed a cup of coffee with the image of a top hat on it. “But it’s very purposeful, and it illuminates something that you’ll be like, ‘Oh! You dirty b******!”

Murphy gave no more hints as to what the top hat might mean, but that was all “American Horror Story” fans needed to start hatching theories about next season. In fact, Murphy’s top hat confirmation led Reddit users to spot the mysterious symbol in a few other scenes throughout the first few episodes of “Freak Show.”

Besides the coffee cup that is handed to Maggie by police officers after they discovered Twisty the Clown’s (John Caroll Lynch) body, the top hat turned up on another coffee cup in episode 2. The scene in question featured a patron of the Juniper diner entering the toyshop looking for the owner. Unfortunately the man and storeowner did not get to enjoy their coffee because Twisty got to them first. The top hat also turned up in episode 2 when Jimmy (Evan Peters) opened up the diner menu when he brought the other freaks in for a meal.

What does it all mean? Ace_VXIII on Reddit posted a theory that the top hat is a reference to Operation Top Hat. Citing a Wikipedia page, the Redditor explained that Operation Top Hat was a “local field exercise” that the United States Army Chemical Corps conducted from Sept. 15 – 19, 1953. Personnel in the USACC were allegedly exposed to biological and chemical warfare in an effort to test decontamination methods – but they were not volunteers and they were not “informed of the tests.”

One of the chemicals that the people were reportedly subjected to was mustard gas. While mustard gas does not have immediate symptoms, those that come into contact with it can suffer from large skin blisters, temporary blindness, bleeding and blistering in the respiratory system, and in some severe cases, death.

Operation Top Hat is certainly a chilling theory about “American Horror Story” Season 5, but viewers have other ideas about what might occur next year.

Another fan took to Tumblr to share his idea that Season 5 will be about aliens. The Matts-Crossing Tumblr page cites Elsa’s (Jessica Lange) last name, Mars, and the town of Jupiter, Florida, as the main clues for an extraterrestrial next season. To further fuel the theory, the fan notes that Murphy did confirm that all the seasons connect – which means it’s possible for the aliens from Season 2 to make a triumphant return.

One Redditor pitched the idea of Season 5 being set in 1920s Atlantic City based on the top hat being connected to the Monopoly character Mr. Moneybags. The Reddit user noted that the Monopoly board is based on Atlantic City, which means the show could focus on the “seedy” and “corrupt” underground world of casinos. Other Reddit users chimed in that the show could introduce the infamous Jersey Devil, which was featured in the intro for Season 3, “Coven.”

What do you think about the “American Horror Story” Season 5 clues? Tweet your thoughts to @AmandaTVScoop.