The Intrigues of Haruhi Suzumiya (涼宮ハルヒの陰謀) (Suzumiya Haruhi no Inbō) is a Haruhi Suzumiya Light Novel.
After closing a time loop fiasco in The Disappearance of Haruhi Suzumiya, our protagonist Kyon is ready to start a new year with a blank slate--no time travel, no apocalyptic worries, and maybe some actual peace and quiet with the SOS Brigade, a club comprised of his high school's most extraordinary students. Their leader is Haruhi, a bold, brash girl who doesn't realize that she's actually a powerful goddess whose moods can easily change the balance of the universe.
Just as Kyon starts to get comfortable, he gets a visit from his friend Mikuru. Except this isn't his Mikuru; it's a Mikuru from eight days in the future! Time traveling shenanigans start all over again as Kyon, guided by the future Mikuru, attempts to stop a terrible future from becoming a reality.
Kyon notices that Haruhi has been lapsing into a state of melancholy, and worries that she might be planning something. On January 2nd, after the events of "Snow Mountain Syndrome", Kyon asks Mikuru to take him and Yuki back in time to December 18 in order to finish what he saw himself doing in The Disappearance of Haruhi Suzumiya. After getting a very abrupt approval from her superiors, Mikuru agrees, and the three of them travel back. Mikuru sees Kyon getting stabbed, and falls apart, trying to help his dead body, while Yuki plays out her role of interfering with Ryoko's dagger. The older Mikuru appears and puts the younger Mikuru to sleep, while Yuki helps turn her former self back to normal.
When Mikuru gets back, she becomes very confused because the only thing she can remember is seeing Kyon get stabbed and falling asleep, and thus she also becomes lost in thought for the next month. Haruhi plans for the SOS Brigade to celebrate the Spring Setsubun festival, along with having the members throw beans out the window and eat fukomaki, a type of sushi (local traditions).
In early February, when Kyon believes himself to be alone in the clubroom, he hears a loud clang from inside the broom closet. When he opens the door to the closet, he sees Mikuru in there - but when the door to the clubroom opens, another Mikuru comes in. Kyon concludes that one of these Mikurus must be from the near future. Yuki walks into the club room and brings Mikuru out of the clubroom. When Kyon brings Mikuru out of the broom closet, he asks what she is doing, but Mikuru tells him that the Kyon from eight days later told her to travel back in time.
Kyon realizes that Yuki knows about this, and had taken the present Mikuru out of the room so she wouldn't discover her future self. Confused about what he has to do and why he sent Mikuru back in time, Kyon opens his shoe locker to leave the school when he finds a note from the future, which he believes is from the future Mikuru that helped him in The Disappearance of Haruhi Suzumiya, asking him to take care of the Mikuru from eight days later. Since the present Mikuru, according to the one from eight days later, had not ever seen herself in the next eight days, Kyon decides that he needs to keep this new Mikuru a secret.
Kyon takes this future Mikuru to his house, where nobody suspects anything because this future Mikuru looks exactly like the present one. Kyon asks Mikuru what will happen during that week, and Mikuru gives him a quick runthrough: During the holidays, the SOS Brigade will go on a treasure hunt with a map provided by Tsuruya, who says that it was left by an ancestor. The Brigade will dig at a mountain behind Tsuruya's house on Saturday and Sunday and find nothing. Afterwards, the Brigade will go on a citywide search. Mikuru also tells Kyon that afterwards, the SOS Brigade will do a lucky draw hosted by Haruhi with Mikuru in a miko costume, when Kyon will ask (almost force) Mikuru to go back in time.
Kyon takes Mikuru to Yuki's house. Yuki tells Kyon that she can no longer synchronize back or forward in time, because she has placed a self-restriction on herself since the events of The Disappearance of Haruhi Suzumiya. She also reveals the name of the entity behind the "Snow Mountain Syndrome" incident: the Macrospatial Quantum Cosmic Existence, an entity of different origin than the Data Overmind.
The next day, Kyon finds two more letters in his shoe locker. The first one tells him to go to a certain place at a certain time and put a certain object there, and that the future Mikuru must go with him. Making the excuse that Shamisen is sick, Kyon finds a way out of attending club that day, and goes to Yuki's house; however, the future Mikuru tells Kyon that she feels uncomfortable around Yuki because Yuki often stares at Mikuru, including when she is trying to sleep and Yuki is standing by her pillow. Mikuru believes this to be because Yuki possibly wants to be like Mikuru, in the sense that she can do what she can to solve a problem without knowing the ending.
Kyon goes over the first note with the future Mikuru, and finds that they are supposed to perform the practical joke in which an empty juice box is nailed to the ground. A man comes and tries to kick the box, and twists his ankle as a result. Mikuru and Kyon help him up, while he calls an ambulance. Since they have accomplished their mission, Kyon and Mikuru try to find a place where the future Mikuru will live temporarily. Kyon eventually brings Mikuru to Tsuruya's house, under the cover story that she is Mikuru's separated-at-birth twin sister "Michiru" who would not like to be seen by the other twin.
Kyon confronts Tsuruya about how much she knows about Mikuru, Yuki, Itsuki, and Haruhi's true identities. Tsuruya answers that although she knows they're not normal, she isn't too interested in the exact details, and is happy watching from the sidelines and seeing others being happy. Kyon meets Itsuki outside, who tells him that the Tsuruya family is supporting the Organization, although the Tsuruya family is not entirely aware of what is going on (much like Tsuruya herself). Itsuki, however, maintains that Tsuruya is a normal human being.
Kyon calls Yuki the next day and tells her that Mikuru will no longer be staying there, and while Yuki denies that she is trying to be like Mikuru, although she believes it is logical for Mikuru to think like that. As it turns out, Yuki was only worried about what would happen.
Kyon reads the second letter, which tells him to scale Tsuruya's mountain and move an oddly shaped rock three meters to the west. They do so, and when Kyon returns "Michiru" to Tsuruya's house, Tsuruya gives Kyon a treasure map, telling him to give it to Haruhi. When Kyon reaches school the next day, he finds three letters in his locker, labeled #3, #4, and #6. Confused, Kyon tries to continue with school, handing the map to Haruhi, Kyon visits "Michiru", and opens letters #3 and #4. Letter #3 tells him and "Michiru" to find an object around some flowers and send it to a certain address. #4 tells Kyon to throw a small turtle into a lake. Not knowing how he would pull these off during city-search days, "Michiru" remembers that Kyon had been paired up with Itsuki, then with Yuki twice on citywide searches when the group split up. Believing this is, by probability, nearly impossible, Kyon believes that he must have asked Yuki to cause this to happen.
The digging for buried treasure starts the next day, and Haruhi has the SOS Brigade dig at a gourd-shaped rock, the same one Kyon had moved before. The Brigade does not find anything as expected, and as they walk home, Itsuki informs Kyon that Haruhi has been stable for the last month. Kyon calls "Michiru" and tells her to meet him tomorrow during the citywide search, and phones Yuki asking her to be in her group twice, to which she assents.
The next day, the SOS Brigade draws their lots, and Kyon ends up with Itsuki as expected. As they "search", Itsuki makes an offer to Kyon: the Organization is offering to pay Kyon a large salary in exchange for becoming an esper, which Kyon firmly denies. During the next city search, Kyon ends up with Yuki, and Kyon asks Yuki to stay at the library while he does his required job with "Michiru". "Michiru" and Kyon go to the designated place, where they find the flowers; however, they cannot find the object, and are instead approached by a strange man who taunts them, says some cryptic things, and makes references to Yuki and Mikuru (especially that he has a bad history with the Mikuru from far in the future) and finally gives them the object they had been looking for before leaving. Kyon deduces that he must be a time traveler.
That day, Kyon goes to the pet store to buy a small turtle, and meets with "Michiru" again, whom he gives the turtle to. He then tells her to meet him at the place where she revealed to him she was a time traveler in The Melancholy of Haruhi Suzumiya. Kyon reads letter #6, which tells him to meet her (referring to the Mikuru from the far future) on the bench once "everything is over".
During the city search, the events play out again: Kyon is paired up with Yuki, and Kyon and "Michiru" go to do their job. When they go to the lake, however, they meet the little boy Kyon saved in "The Melancholy of Mikuru Asahina", who asks if he can take care of the turtle. Realizing that his instructions only told him to drop the turtle in the lake and gave no ideas about what to do next, Kyon drops the turtle in the lake and, once it walks out, gives it to the boy with the instructions on how to take care of it. He then tells the boy not to tell Haruhi about this.
However, as Kyon and "Michiru" walk away, "Michiru" is kidnapped by a bunch of people in a car, and Itsuki calls Kyon telling him that "they" are on their way. The "they" refers to Arakawa and Sonou Mori, who take Kyon into their car and chase "Michiru"'s kidnappers in a car chase. Mori reveals to Kyon that the kidnappers were probably a group that consisted of a group of espers hostile to the Organization, time travelers who wanted to use "Michiru" as a bargaining chip with the future authorities, and an entity of aliens different from the Data Overmind. She also reveals that the purpose of "Michiru" being in this time period was to make sure they didn't kidnap Mikuru right in front of Haruhi. Arakawa and Mori eventually corner the kidnappers, who include the strange time traveler man who had taunted Kyon and a strange woman about Kyon's age. The group easily releases "Michiru", and Kyon takes her back to the library, where he finds that Yuki has received letter #5. Yuki follows the letter's instructions by waking "Michiru" up from the drugged sleep her kidnappers put her in. Kyon then sends "Michiru" back to her original time.
The next day, Haruhi calls the SOS Brigade to assemble and try to dig again, something unexpected for Kyon as "Michiru" had never mentioned that. However, it turns out to be a surprise for the boys, as the girls had secretly gotten together and made chocolate for them. Kyon realizes that moving the rock had not only given Haruhi a new place to hide her chocolates but had also prevented her from finding a real artifact. Kyon meets the future Mikuru at the appointed time, who tells him that the man who went to the hospital was supposed to meet a woman there and raise a family with her, while the strange object was supposed to give someone the idea about time travel, while the boy who saw the turtle saw the ripples it made in water and used it to make a theory about time travel, leading to the invention of the TPDD. The future Mikuru warns Kyon that he will soon have to make a choice that could severely change the future. Kyon realizes that the future Mikuru had been toying with her past self, forcing her to watch history as it happened. He tries to show his resentment against the future Mikuru, only to find that she has disappeared back to her future, leaving a box of chocolates.
Kyon tells Tsuruya to dig three meters away from the rock, where she finds a strange device with circuits, made from a titanium-cesium alloy which was impossible for her ancestor to make during that time, and thus suspects it must be from an alien or time traveler. Haruhi begins her lucky draw, and Kyon gets Mikuru to go back in time eight days and help out his past self. Immediately, Mikuru comes back, telling him that she's back.