Before a reader will believe your plot and story, they need a good reason to buy in. Plots that have a guess or a misconception at the heart of them are very difficult to pull off because there is not a lot for your reader to hook into and believe in. Let’s say that you’re writing a book where a girl goes after a boy because she thinks he is the serial killer terrorizing the town. Thrillers are more popular on shelves today and this is a premise that’s bound to have some romantic tension. Great.
But the author in this example must do a lot of work at the beginning to make sure that her guess seems reasonable and logical to the reader. “I just knew it in my bones that he was the Shady Pines Strangler” isn’t going to convince your reader to go along for the ride. Telling isn’t going to do it. Something needs to happen in the action of the plot that makes your character–and, by extension, your reader–sure. A tangible event or something seen with one’s own eyes is as close as you can get to concrete facts in fiction. So your audience will need nothing short of that to be convinced that your protagonist is on the right track…and to want to follow her on the plot.
The same goes for misunderstandings and misconceptions. It is very difficult to suspend disbelief and follow a plot that hangs on a misunderstanding (that’s why characters in denial don’t work well). Especially if the reader knows that the character has made a mistake. Let’s just give a quick example here. A girl is in the cafeteria and a boy yells out that she looks like a fat dude in a monkey suit. She spends the rest of the story building a complex revenge scheme to humiliate him…and it turns out that, the entire time, he had been hollering over her head at a fellow basketball player. They laugh about it and, surprise surprise, fall madly in love and wear gorilla suits to their wedding, etc. etc. etc.
Despite the sarcastic ending to this pretend tale, I hope you can see why it wouldn’t be satisfying. The misunderstanding bit is way too weak to pin an entire plot on. This is extremely prevalent in romantic comedy style novels, so if you’re writing one, make sure you’re not relying on this trick too heavily. Weak plot also comes from character guesses that aren’t backed up by concrete evidence via action or something that happens in the physical realm of the story. In a fantasy novel about faeries, you can’t just talk about faeries for the duration of the book, telling over and over again about the magical atmosphere in the woods. If there are faeries, we better see some faeries. If the hot new guy in school is a serial killer, we better see brown traces of dried blood under his fingernails and smell a suspicious odor coming from the trunk of his car.
Otherwise, in both cases, your readers might see your character as jumping to conclusions…and you don’t want to make them feel like they’re going on a wild goose chase. With everything you write, you should make their investment in the plot more, not less.