THE MOUNT CHILIAD MURAL
The mural features a glowing eye and a series of connected boxes marked with an X. At the bottom of the flowchart structure are three boxes showing (what looks like) a UFO, an egg and a man with a jetpack. The consensus is that these are the prizes for solving the puzzle: a UFO you can pilot, a jet pack (like Grand Theft Auto: San Andreas' greatest gadget) and, er, an egg. This is the weird bit, with some suggesting you'll unlock a dinosaur (mental and unlikely, but you can see a T-Rex shadow on one face of Mt Chiliad) - or, more likely, some kind of alien egg.
The glowing eye and lightning emerging from the sides suggest a link to the Illuminati (arguably the real world's greatest conspiracy theory), variously linked to major religions, global political control, finance and - of course - aliens. Franklin's house contains an Illuminati-style poster, and there are similar symbols all over Los Santos; the significance of which is still being debated.
Initially, it was felt that the mural represented a cross section of Mt Chilliad, with each box representing a hidden location. However, compelling evidence suggests the mural should be overlaid on the game map, with the shining eye on top of the north coast - the exact placement is still being debated. See below.
THE EVIDENCE
UFO 1
Under the Mt Chilliad cable station, there's a hidden message urging you to return when you've completed the game 100%. Once you've done so, you need to stand on the peak of Mt Chilliad at 3am during a thunderstorm or when it's raining. It sounds ludicrous, but you'll see a huge UFO, lights blazing with an eerie noise. You can't shoot it and the characters don't acknowledge it, but it's a 1960s style UFO with - weirdly - FiB on the side. Many speculate the UFO is a hologram (a clue to start the UFO hunt) and there's some shaky cam off-screen evidence to support it.
UFO 2
In Fort Zancudo, on the far west coast, there's a mysterious bunker that emits glowing spotlights at certain times in the night. Eagle-eyed players took this as a clue, and ascended over this spot in a chopper. Lo and behold, if you climb to the horizon limit (when the words 'San Andreas' appear in the bottom right location indicator), you can see an industrial-looking black UFO, with moving 'claws'. It's tricky to pinpoint, so move around until it materializes in a blur of pixels - and don't fly below it or your chopper shorts out. It looks like a more evil and industrial UFO, in line with movies like District 9 or Independence Day. You can't destroy it, but you can land on its forcefield and walk about, perhaps as part of a glitch. Once again, you get no trophy or on-screen acknowledgement for finding it.
UFO 3
There's a barely-hidden monument to the north-east of Sandy Shores, covered in graffiti and references to aliens - with a picture of a 'Grey' alien and words like 'Beam me up'. If you fly above this location in a chopper, or slightly to the north of it, you'll find another hidden UFO. Again, it's fiddly and you need to break the horizon line. You'll see nothing until it suddenly 'pops' into view. This grey UFO is 'older' and looks just like the hologram UFO from Mount Chiliad - also with the FiB logo on the side. The inference is that GTA V's version of the FBI are part of the conspiracy, with possible links to the Illuminati. *Head spins*
UFO 4
Some speculate that this is where the glowing eye of the mural needs to be placed in order for the map hints to work. Either way, to the north coast of Los Santos, above Paleto Bay, you can use your submarine to find a UFO at the bottom of the ocean. It doesn't do anything, and some think this is the UFO that becomes flyable later on.
THE BLACKLIGHT MAP
The GTA V Collector's Edition contains a blueprint map with hidden text on its rear side - but you need to use a UV / blacklight lamp to reveal it. You can see the hints in the image below. Don't ask us how anyone found this in the first place ("Ooh, I must inspect that with an industrial UV lamp I had lying around...") - but it's possible they add another layer to the puzzle. Many clues relate to hidden spaceship parts that you need to collect to obtain 100% completion, but some are more abstract.
For example, the prison near Sandy Shores is circled, with the words '9A'. This almost, but not quite, matches a hotspot from the mural map, so it could be an alignment issue - but we don't know. Either way, when you fly into the prison, starting an instant four-star wanted level, you can see detention block 9A in the middle. We've explored it repeatedly and can't find any hidden entrances, but some say there is a scrawled clue for a graffiti part. More likely, block 9A relates to another - possibly related - conspiracy theory about a mass murderer.
THE MASS MURDERER MYSTERY
There's a poem you can find in the national park that relates to the serial killer and note pieces. It says:
One is done
Two was fun
Three tried to run
Four called mom
Fives not alive
Six is nix
Sevens in heaven
8 won't wait
The inference is that each entry relates to a murder victim. There's another set of writing in the national park. It says -
They want me. They can have.
But they'll never get my people.
Even though I shall leave them sign enough.
Where they put me.
This reads like the final confession of the killer. But where did they put him and what signs were left? The belief is that they put him in prison cell 9A where there's another note on the wall that you can read below.
Note the scrawled half-finished '8s' that look a bit like the UFOs on the blueprint UV map (possibly a co-incidence), plus the drawing, which very closely resembles the far north tip of Los Santos and its islands. The text clearly references a volcano, but the 'infinite eight' bit deserves further inspection. Is it 'infinite' as in eternal or undead? Does this reference UFOs, or some form of cult like the Epsilon Program or the Illuminati? Are they aliens or cult members sacrificed for some higher goal? We don't know, and it might be a separate mystery - but it needs to be solved.
SO, WHAT'S NEXT?
We need to find the remaining two (maybe three) clues on the mural map, which might be further UFO sightings - or something else. These may require the use of specific characters, and unique circumstances (e.g. weather or time, like the hologram). One theory is that a character needs to be abducted by the UFO above the Sandy Shores monument, since this UFO has a hatch that opens and closes, with glowing lights. In-game radio makes reference to UFO abductions, plus there are graffiti hints.
There's also a weird clue on the blueprint map, with the words 'Shoot for the stars' next to the UFO-shaped squiggle. Perhaps you literally shoot at the stars from this location with a sniper rifle (previous GTA's let you shoot the moon and alter its size). Or perhaps the solution is more oblique, and the stars reference celebrities. Do you have to target a celebrity who's part of a cult?
