Game of Thrones Season 7 has been moving at a relentless pace but one key Westerosi figure has got the short shrift: Littlefinger. In the early years of the show, Petyr Baelish marked himself out as one of the most devious schemers in all the Seven Kingdoms, but since seizing control of the Vale has taken a back seat - and now that object of affectionate manipulation Sansa Stark is wise to his tricks he seems utterly neutered, walking around Winterfell spouting random advice while the younger generation take on old and new fights.
To many fans, his days seem both numbered in the most mundane ways. Sansa's playing the game and clearly knows the whisperer is rather worthless, while Jon is only keeping him around to ensure control of the strong armied, heavily protected Vale; Petyr's really not got many acquaintances left to butter up. He's back trying to manipulate the Starks, but this time it's unclear how successful he'll be. And it definitely looks like his previous misdeeds will soon come to light.
Littlefinger's Secret Role In Joffrey's Death
At the end of "The Queen's Justice", the Lannister army performed a massive coup against invading Daenerys Targaryen: they willingly lost home Casterly Rock so the Greyjoy fleet could decimate what remains of the Mother of Dragons' sea force and instead led an attack on the undefended Highgarden, home of House Tyrell. This wasn't a total victory for Kingsguard and General Jaime Lannister, however, with Olenna Tyrell - the last member of the line after Cersei blew up her son and grandchildren in the Sept of Balor last season - revealing with her dying breaths it was she who killed King Joffrey.
Cersei and Jaime's psycho offspring-of-incest was murdered at his wedding to Margaery Tyrell; he was poisoned using a crystallized substance smuggled into the wedding unwittingly by Sansa Stark and put in the King's wine by Olenna. However, she wasn't working alone - the whole scheme was enabled by a far off figure: Littlefinger. Petyr had at this point been sent to the Vale by Queen Regent Cersei, but seeing Joffrey would soon be more reprehensible and dangerous than the Mad King helped to usher in Tommen's reign; he had Ser Dontos Hollard plant the poison on Sansa and engineered Stark's escape.
And he pretty much got away with it. Tyrion took the fall and while he eventually escaped execution (taking down father Tywin in the process) he is still widely assumed as the culprit - he was found guilty in a trial by combat and is now Dany's Hand, fully betraying his homeland - as Cersei cited in the Season 7 premiere. Most of the people who know the truth (in the show at least) are all dead: Olenna and the Tyrells have been wiped out for unrelated reasons and Littlefinger murdered Lysa Arryn himself; only Sansa certainly knows the truth. This was all part of Baelish's plan - he purposely made himself a passive element leading up to the murder - although he's got particularly lucky with Olenna, who once threatened to grass him in should her House fall.
Will Littlefinger's Scheming Be Revealed To The Lannisters?
However, while her confession doesn't directly implicate Littlefinger, it brings the conspiracy to which he was integral to light. Jaime already knew Tyrion didn't kill Joffrey and now has pretty unavoidable evidence of a bigger plot. The only other person who's been seriously linked was Sansa, who left the wedding during the fracas and is still implicated as Tyrion's accomplice (she disappeared and was in hiding as "Alayne Stone" in the Eyrie before returning to Winterfell - first as captor, now victor). But even then, Jaime will know there's more to it than that - suspicions that could very easily lead him to Littlefinger: many wanted Joffrey dead but few are like Petyr and would act on it.
If this comes out it could singularly tear the realm apart due to how ingrained Baelish is. We know from how she handled Elaria Sand that Cersei is still vengeful over her children's deaths, so would likely declare active war against the North - for housing Littlefinger and Sansa's proxy involvement - catalyzing Jon and Dany's situation, undoing their new wight scheme and stretching a Winterfell preparing for a totally different war to the North. Littlefinger's prided himself in his outwardly impartial approach, but now he's at the home of people who despise him yet it's the safest place in an army of enemies.
However, this reveal seems to have been tempered - Jaime revealed Olenna's confession to Cersei, which she believed, and the show moved past it to bigger Lannister family issues. If Littlefinger's brought down, it's looking like it'll be to do with his part in the biggest unresolved murder in Game of Thrones.