Spot the lies, then “Hunt the Truth in Halo 5, where the truth is never what it seems”
Do you like solving mysteries? If yes, this is for you. If you’re more like Buck and “love being an ODST, point and shoot, none of this gray area BS”, this may not be quite your type of thing. At some point, I’ll put up a summary of the main ideas of the hidden story for those who just want the main ideas.
Halo 5 Story Type
Halo 5 has a “surface story” (which you probably all know by now), and underneath it, a hidden story - a Mystery to solve called “Hunt the Truth”. Okay, 343 didn’t include an obvious instruction booklet, but they did say “Hunt the Truth” enough times (which did suggest there were lies in the game, maybe even a big ONI cover-up). They also helpfully hid some guides and lots of clues in the Campaign, with some more clues in the trailers. Some are easy clues, though some are much harder to get.
You can solve Halo 5’s main Mystery in-game without wider Lore, but Lore can add more information and the right bits of Lore, can add even greater depth to the story. Trust me when I say it does and will all make sense. It’s worth the effort, and the outcome is stunning!
Now you know this, I hope you will feel more confident that you were always on the right track when you questioned the story. It’s not 343’s plot that’s “poor”, it’s that “surface story” that’s “full of plotholes”, mainly because of the lies in it. Compare the Locke and Master Chief Trailers (see YouTube). Locke makes statements (like the player who’s tricked into believing the “surface story” and its lies), but Chief asks question after question. So, if you’re asking questions, you’ve stopped playing like Locke, and are starting to play the game like Master Chief! As the TV Trailer says, “When he recruits others to join him…”, do you want to join Blue Team to help Chief “Hunt the Truth”? You do? 
Tips
The Cortana Mystery - The Central Mystery in Halo 5
In Halo 5, we meet an AI claiming to be “Cortana”, which raises an obvious question.
Did Cortana survive Halo 4? There’s two basic answers, yes or no, so we have two characters:
Locke’s point of view “Yes! Cortana is alive, on Genesis, leading an AI Revolution, and launching the Guardians”. (This is Locke’s Visor viewpoint).
Chief’s point of view “No! I watched her die! It can’t be Cortana! Can it? Oh, but wait! What if she is?”. Yes, Chief is fairly certain Cortana is dead, but he has doubts, and this is what drives him to find out, just like we need to. (This is Chief’s Visor viewpoint).
What are the possible outcomes?
(a) If Locke is right - the “surface story” is all true, and Cortana is behind the AI Revolution and the Guardians.
(b) if Chief is right - she’s a fake, so who is behind this plot?
(c) if they’re both right - someone has resurrected Cortana, but have they reprogrammed her, or are they controlling her somehow, and who is behind this plot?
(d) if they’re both wrong - that’s not Cortana on Genesis, but nor is the real Cortana dead! But who is behind faking Cortana, controlling the AI’s and Guardians?
Unless the surface story (a) is true, then in all the other answers (b) to (d) one theme emerges - Cortana is being framed to cover-up someone else’s plot to grab the Mantle and rule the galaxy!
Chief’s Character Development
As you “Hunt the Truth” about Cortana, imagine what effect any of the last three answers above will be having on Chief. On top of everything else they did together, he believes he watched Cortana die saving him and the world at the end of Halo 4. If he now finds out someone is covering up their plot not only by trying to frame him, but also by framing his dead best friend Cortana…
Round Up The Usual Suspects!
If there is a deeper hidden plot, then who could be behind it all? In Halo 4 and the Lore afterwards, after the Didact revealed the Mantle of Responsibility and was then taken out of the way as he treid to claim it for himself, the main battle for the Mantle was between ONI and Jul Mdama’s Covenant. Did one of them finally succeed, or has someone beaten them to it? Even within ONI, it could even be ONI Rogue Agents, or Covenant double-agents within ONI. But there are still other suspects on the list, including the Didact, Colonial Rebels, or even the Flood.
Hopefully this will make more sense as you play the missions in Halo 5, as you see the battles between ONI and the Covenant in a race for the Guardians and the Mantle.
Good Hunting, Spartans!
The clues and answers are all in there, somewhere. Use what you see and hear and the Intel to rule out the false leads and lies, and find out the truth about what really happened to Cortana, if she survived Halo 4 or not, and if she did, is she being controlled, or has she been replaced by a “Cortana Mk.2” look-alike? As well as Chief, is Cortana also being framed to cover up someone’s devious plot to grab the Mantle?
Spot the lies, then “Hunt the Truth in Halo 5, where the truth is never what it seems”?
