Spoiler Alert.... That 1st Still...Marty's Youngest with Yellow hair? Ok, I just need to wait on the next episode before anymore speculation. LOL
Likely from someone with shit else to do other than watch it all 6 times over. Also remember: Daughters room... and Zackly! Best hour of television since Walter White died and the subsequent final to this years Boardwalk Empire. This is tremendous filler.
Why did Maggie cover up the affair? I know why Marty covers for Rust, it's because Marty basically murdered Ledoux. Here's my take. The Carcosa society (tuttles, even that smug State Trooper) is trying to summon Cthulhu by sacrificing children. If you read any of Lovecraft's work, (let's be clear, True Detective was a pulp mag, HP Lovecraft's Weird Tales was also a pulp mag) you know that Cthulhu is worshiped in Haiti, and Louisiana. So this Carcosa society in my opinion is trying to reenact the King in Yellow, and summon Cthulhu by sacrificing children. Is Marty, Maggie, or even their daughter mixed up in all this? Maybe, but Marty is way too stupid in my opinion to be involved. One thing I do know is I really have no idea where they are taking this, I just think I have an idea.
There is no supernatural twist. The original script had no mention of "Carcosa" or "The Yellow King". It was added later as an idea of a story within a story that made people go mad. There have been no signs of the supernatural thus far and we're 75% complete with the season. To make it supernatural at this point would ruin it. Maggie is a cop's wife, so naturally she doesn't trust cops. Better to side with the evil you know than the evil you don't know. I'm not so sure that there is a literal "Yellow King". I think it's an idea...
I'm not saying that there will be a supernatural twist I'm saying this cult believes in Cthulhu, and The King in Yellow. They wouldn't add in all this Lovecraftian and Chambers shit without there being a point. It isn't just for cool dialogue.
To cover her own involvement? Breaking up their partnership drops a set of eyes so I am inclined to believe she has a dominant role in the discovery. You could be right. I still can't rule him out but his "in" may be limited to the reality that it involves his wife/ daughters/ in-laws. The spoiler in the link you provided is kind of leading me in that direction. Maggie's father despises Marty for everything but his hidden truth. Could be this is the "right under my nose" investigation reference he over emphasizes early in the series. I think that speaks for everybody. Brilliantly edited for the series but it kind of makes you want to beg for the shit that got cut. There is still a lot of story left and anything speculated at this point could be considered a foregone conclusion. That is ultimately the beauty of this series. I am a sucker for "who done it" series and now I hate shows where investigations are wrapped up in under an hour. The AMC series "The Killing" was equally as brilliant where as it took 2 seasons to decide the killer. The viewer gets to invest more time with the characters and their own story. Who a person is and how that person investigates can be miles apart from douche bags series like CSI (pick a city) and their absurd portrayals of actual human beings. Conclusions are inherent of the person finding the culprit and in many cases, it takes one to know one.