Huge spoilers, obviously. So I'm not going to print anything before a huge warning for that reason but, if you wanted, you could potentially read Game of Thrones season 7's entire plot right now.
The information originally appeared on the Free Folk reddit which has managed to be incredibly accurate spoilering through most of season 6. The account that posted it has already been deleted but other posts have collated the information. You can also read an episode by episode breakdown on Heat Street if you really want to spoil everything.
As well as the reddit's strong former track record for successfully unearthing spoilers and plot details, Nathalie Emmanuel, who plays Missandei tweeted this out:
It's really disappointing there are people who are determined to ruin Season 7 for everyone... 😒 #spoilsportsOctober 22, 2016
A few people are saying (hoping) she might be referring to a flood of set pics that have been appearing during filming. However, that's been happening for weeks and the reddit post is pretty much as big as it gets if it's true, so many are assuming that's what she's talking about.
Okay, warning time: The entire suspected plot of Games of Thrones season 7 will appear after the Hodor.
Okay, here's an abridged version of the season 7 plot taken from this reddit post that has linked together all the leaks, set photos and info out there so far.
The White Walkers marching South towards the Wall.
Bran crosses the Wall, meets with Edd. (Bran was at the studio filming with other "Team Starks", though apparently he was filming a scene at the Castle Black that day.)
Jon receives a raven from Dany, she's summoning the lords of Westeros. Jon and Davos decide to go because they need the dragonglass from Dragonstone.
Jon leaves Sansa in charge of Winterfell.
Jon leaves Ghost at Winterfell, where he stays all season.
Jon and Davos arrive at Dragonstone. Tyrion meets them on the beach, and the Dothraki take their ship. (Jon, Davos, Tyrion, Missandei have all been filming together in Bilbao- widely believed to be the set of Dragonstone.)
Tyrion brings them to meet Dany, encountering Missandei and Grey Worm on the way. The "throne room" contains a number of Dothraki. (ALL have been spotted filming in Bilbao - widely believed to be the set of Dragonstone.)
Dany and Jon meet. Dany demands he bend the knee, which he refuses. Evidently, he discusses the WWs, but she doesn't believe him. Tyrion insists that Jon isn't crazy.
Davos tries to mention Jon's resurrection, but Jon dismisses it.
Dany respects Jon immediately, Jon to Dany maybe not as much?
Bran arrives at Winterfell. Meera returns home. (Bran has been spotted on set with other "Team Starks")
Arya arrives at Winterfell. (Arya has been spotted on set with other "Team Starks")
Sam leaves Oldtown for Winterfell with Gilly and baby Sam.
Jorah reunites with Dany at Dragonstone.
Jon receives a raven telling him that Bran and Arya are at Winterfell.
Jamie, Bronn, Tyrion and Davos have a secret meeting at some point where Tyrion tries to persuade them to surrender to Dany, which Jamie ignores. Unclear if this happens before or after Dany ambushes the Lannister army. (Footage has been captured of Peter Dinklage and Liam Cunningham filming together, appearing to be preparing a boat to leave the beach. This might be them preparing to leave for the meeting. Another boat-beach scene has been captured filming, again including Tyrion and Davos, but also Gendry!)
Gendry's in Kings Landing making weapons, and he is found by Davos. (Tyrion, Davos and Gendry have been filming together on a beach in Bilbao.)
The party travels to Eastwatch-by-the-Sea by boat. Davos stays behind while the others go wight hunting.
Jon leads a small force (himself, The Hound, Beric, Thoros, Tormund, Jorah and Gendry (WHY?!) to capture a wight. (Scene set to be filmed in Iceland in January includes 6 major characters.)
The team is attacked by the Night King's army, including a wight polar bear. The bear kills Thoros (apparently a slow death). (Thoros is confirmed to return for season 7.)
They are surrounded on an island on a frozen lake and are nearly overcome when Dany and her dragons show up. She flies most of the team back to Eastwatch, but Jon is left behind.
Jon is almost killed, but Coldhands/Benjen arrives and sends Jon off with his horse while continuing to fight the horde. Jon watches Benjen swarmed by undead as he rides, half dead, to safety.
Viserion is killed and raised as the Night King's mount.
Jon offers to lay down his title as KITN if Dany and her forces will help against the WWs. This scene is private.
Sansa sentences Littlefinger to death, which Arya carries out.
Cersei awakens in a bed soaked with blood. The general consensus is that she miscarries.
Sam and Bran figure out Jon's heritage. He is apparently a legitimised Targaryen named "Aegon".
Jon and Dany have sex for the first time on a boat headed North.
The Wall falls at the end of the episode. The Night King attacks the Wall with the reanimated Viserion. He now breathes blue flame.
Game of Thrones season 7 will debut in summer 2017.