Motive Misidentification

Disgusted by the Big Bad's squirrel-stealing antics, Steven Ulysses Perhero finally corners the dastardly villain in the Abandoned Warehouse, where the following dialog takes place:

"Steven Ulysses Perhero: Evil Overlord! Those squirrels have suffered enough! I won't let you sell any more of them for medical experimentation!!! The overused exclamation points show my fierce-- Evil Overlord: Medical experimentation? Is that what you thought I've been doing? You fool! What's going on here is far more brilliant! I'm using the biological power of the squirrels to power my Death Ray!

Steven Ulysses Perhero: You Magnificent Bastard!"

What a shocking twist! The hero... and naturally we the audience... assumed the villain was up to something. And we were correct. He was. Unfortunately, the hero... and naturally we the audience... were utterly incorrect about precisely what the villain was up to.

This happens a lot when your hero is either too eager... or simply an idiot.

Basically, this trope is when a character comes to an erroneous conclusion about a villain's motives based on his actions. While the Big Bad is certainly still a horrible person, how he truly intends to go about it or why he's going about it in the first place turns out to be something we were way off the mark for. And sometimes, the evil scheme isn't actually an evil scheme at all. In either case, the Big Bad didn't try to fool the hero, or leave a false trail, or otherwise trick him in any way. No, with this trope, the hero was fooling himself all along.

Sometimes the result of paying attention to the Red Herring. Compare Hidden Agenda Villain. Contrast Evil Plan for a more obvious motive though this trope sitll might occur. See also Not Me This Time.

This is an Ending Trope, so expect UNMARKED SPOILERS.

Anime

 * Happens in Fullmetal Alchemist, when Dr. Marcoh asks Envy if they're planning to Envy responds: "Oooh, so close. But that's not it." It turns out their plan is
 * Played for Laughs in Ranma Half.  Taro arrives with a grudge against  . The audience is led to believe his grudge is his One-Winged Angel cursed form   however he actually enjoys its enhanced power, and his true grudge is

Comics

 * Mister Fantastic makes this mistake with Doctor Doom all the freaking time.
 * In Watchmen, Rorschach is convinced that someone is trying to take out all the former vigilantes when the Comedian is found dead. His killer's true motives are different.
 * Not a typical example, in that, the villain/antagonist actively worked to make this "Mask Killer" theory seem more credible once they heard about Rorschach's theory, expressly to obfuscate the true plan long enough to pull it off.
 * Spider-Man once tracked down Doctor Octopus through various thefts, only for Doc Ock to give up once his experiment failed. The real motive wasn't criminal; Doc Ock wanted to create a cure for cancer to save an old flame.
 * In Sleeper, TAO's motives are completely unknown to the characters, and the readers are led to believe he's running an incredibly complex Gambit Roulette to try to Take Over the World. It turns out

Films -- Animation
"Randall: (chuckles darkly) You still think this is about that stupid scare record?
 * Randall in Monsters, Inc.. Mike thinks he's trying to cheat his way to the all-time scream record, when he's really up to something much worse...

Mike: Well... I did. Right up until... you chuckled like that, and now I'm thinkin' I should just get outta here."

Films -- Live-Action

 * In Hot Fuzz, Nicholas Angel believes the murders in Sandford were happening as part of a very lucrative property swindle. In reality, the fact that all the murders that occurred since he arrived in Sandford were tangentally connected to a land swindle was a coincidence. They were really taking place because the victims were a threat to the town's title of "Village of the Year"....and they had been going on for years, with scores and scores of victims, and an entire conspiracy of murderers.
 * Note that many of the movie's deleted scenes would have served to further expand on that Red Herring and explain how it was going on.
 * In the orignal Die Hard, John McClane, the LAPD and FBI are led to believe Hans Gruber and his men are terrorists, holding the Nakatomi Plaza building hostage in exchange for numerous terrorist prisoners being released. In reality, Hans is deliberately leading the FBI to believe this, as the FBI's protocols for dealing with a terrorist threat are exactly what he needs to rob the place, and get away with the cash.
 * This is repeated with Hans' brother in Die Hard With a Vengeance where he first leads authorities to believe that he's a terrorist who wants revenge on McClane, but is actually using the confusion to set up a huge robbery. The fact that he would also get revenge on the cop who killed his brother was just icing on the cake. He then almost convinces the world that he carried out the robbery in order to destroy the gold rather than keep it.
 * In Pirates of the Caribbean: On Stranger Tides, everyone assumes that the Spanish are racing towards the Fountain of Youth in order to attain immortality. In fact,.
 * Which makes them arguably
 * In Psycho when Marion's sister and fiancee become convinced that both Marion and the Private Detective they hired were both killed at the Bates Hotel, they're sure that Norman Bates robbed Marion and then covered it up. In reality, of course, Norman is just crazy and never even knew about the money that Marion had.
 * In Goldmember, Austin Powers find Mini-Me at his apartment with what looks like a knife, and comes to the conclusion that Mini-Me arrived to assassinate him, thus causing him to fight him. In actuality, the "knife" was actually a letter opener (Mini-Me, when Austin was entering the room, was trying to open an envelope that the mole gave him), and Mini-Me's real reason for his presence at Austin's apartment was to defect to his side.

Live Action TV

 * Happens from time to time in Leverage. In their Christmas episode, they believe that the plot at the local mall is to steal everyone's credit card numbers for massive identity fraud. So they shut down the power in the whole area. Then it turns out that the Magnificent Bastard behind it wanted them to do just that. The power outage disabled the security system at the nearby bank (their real target) and he and his goons were free to move in and rob it. Of course, this being Leverage, they were still able to stop him in time. Still one of the only times when the villain was a step ahead of the team.
 * In the Buffy the Vampire Slayer episode "Earshot," Buffy finds Jonathan in the school bell-tower with a high-powered rifle and immediately assumes he's out to perpetrate a student massacre, and gives him a whole speech condemning it. A confused Jonathan replies that he came up there to kill himself.
 * Occurs from time to time in Law and Order: In "Doped", the prosecutors assumed the defendant spiked the victim's nasal spray (which caused her to have a car accident that killed herself and seven others) to try and discredit her whistle blower testimony and protect his employers. Turns out, he did it out of outrage that she wasn't going to keep any of the reward money she'd get with a successful action against their employer (a pharmaceutical company pushing an expensive, but near-useless cancer drug with false advertising.)

Literature
"Erik Lönnrot: Scharlach, are you looking for the Secret Name?”
 * In The Adventure of the Yellow Face, Sherlock Holmes misidentifies his client's suspicious wife's motive, and is for once proven wrong. It turns out that there was nothing villainous about the wife's true motive.
 * Harry Potter and The Chamber of Secrets: Harry and most likely everyone else assumes the heir of Slytherin has reopened the Chamber to carry out Salazar Slytherin's mission to purge Hogwarts of Muggle-borns. When Harry meets the Heir of Slytherin, Tom Riddle, a.k.a. Voldemort explains that his target all along has been Harry. All the near-killings were bait.
 * Also in Goblet of Fire, the heroes initially suspect that someone entered Harry's name in the Triwizard tournament in order to get him killed while competing. The truth is
 * The Death and the Compass, a Genre Deconstruction of the Detective Fiction by Jorge Luis Borges

Scharlach remained standing, indifferent. He had not participated in the brief struggle, and he scarcely extended his hand to receive Lönnrot’s revolver. He spoke; Lönnrot noted in his voice a fatigued triumph, a hatred the size of the universe, a sadness not less than that hatred.

"No,” said Scharlach. “I am seeking something more ephemeral and perishable, I am seeking .."

Video Games
"Clank: There must be a better way to find a home for your people! Drek: Fool! You think that's what this is about? Who do you think polluted the last planet? I did. This is about one thing and one thing only: cash! And lots of it. You see, I've been paid for every square inch of my new planet. Once the inhabitants move in, I'll begin polluting this planet as well! And the whole thing starts all over again. Aah. Brilliant.
 * Altair of Assassin's Creed accuses Majd Addin of murdering ordinary people simply for believing differently than him. Majd Addin corrects Altair by telling him he did it because he could, and because it was fun.
 * In The Legend of Zelda: Wind Waker, everyone believes Ganondorf has returned to destroy the world. It turns out that he originally wanted to take over the lush Hyrule to free his people from the harsh desert. It's quite sad, really.
 * Magus from Chrono Trigger is a send-up of Japanese fantasy RPG tropes: as the Fiendlord, he sends forth his monstrous armies in a bid for world domination. He's also identified as the creator of Lavos, the titanic hellspawn fated to destroy the world in 1999 AD. Crono and company set off to defeat Magus and prevent him from triggering the end of the world; unfortunately, it turns out that Magus was actually trying to destroy Lavos all along, and they interrupt him just in time to hasten Lavos' awakening, putting the world on schedule for destruction in 1999 AD.
 * This happens in the climax of the first Ratchet & Clank, when the title duo confront Chairman Drek as he's about to destroy Ratchet's home planet to make room for the Blarg's new planet (the raw materials of which came from the destruction of several other inhabited planets).

Clank: Y-you evil little--"

"Nefarious: Vengeance? You think I went to all this trouble for mere vengeance? *to self* And they say I'm egomaniacal."
 * Also happens at the very beginning of A Crack in Time as a subversion of sorts, when Clank accuses Dr. Nefarious of seeking vengeance.

Web Comics
"Xykon: I went to steal it from that librarian in Cliffport, and it turned out oops! He was also an archmage! Needless to say, hilarity ensued."
 * Order of the Stick: Xykon murdered Roy's father's master and took his crown. Roy thought he did it because the crown was magical and powerful; it turns out, it's neither of these things. Xykon just wanted the crown because it looked cool.
 * The Sapphire Guard believes the Bearer of the Crimson Mantle's goals are to destroy the universe. While an acceptable loss, the reality is that he is actually out to blackmail the gods for his species' dominance over others. Or fair and even treatment. He'll settle for that, as well. Though it's that or the end of the universe...

Western Animation
"Luthor: President? Do you know how much power I'd have to give up to be president? That's right, conspiracy buff. I spent $75 million on a fake presidential campaign, all just to tick Superman off."
 * In Justice League Unlimited, the Question confronted Lex Luthor about Luthor's current evil scheme. The Question thinks Lex was trying to discredit the League in order to win the presidency; a Lex Luthor from an alternate universe had done this, killed the Flash, leading to that universe's League going rogue and becoming Evil Overlords. Question went to kill Luthor (because he was known to be insane, so the League's reputation wouldn't suffer as much); unfortunately, Luthor reveals he has superpowers, and proceeds to beat the tar out of the Question, at the same time revealing his whole presidential bid was just a ruse to tick Superman off. The Question wasn't even close.


 * One episode of The Mask featured a dognapper and a chili maker who bought the abducted dogs. Stanley thought they were turning the dogs into chili but he later learned they were just having the dogs try a new brand of dog food.