All caps. Don't forget it. In the introduction, we find out that there is such a thing as real witches. Our narrator prepares us for a world where witches exist and, to make matters worse, it sure isn't easy to recognize them.
The big issue here is that witches like to do away with children (and that's putting it lightly). This is not cool – at all. It needs to be stopped. Without this conflict there wouldn't be a problem. Witches existing isn't necessarily a problem. Witches killing children definitely is.
This is a life-long complication – literally. The Grand High Witch turns our narrator into a mouse, which will make it kind of tough for him to solve the initial problem – not impossible, just tough. As if the conflict (i.e., witches want to kill children) wasn't enough, this just makes it even more of a challenge.
After our narrator has successfully poured the Mouse-Maker formula into their food, all of the witches start to transform into mice. It's really quite intense. One second they're gobbling up their soup and the next second, they're mice. Then everyone in the hotel goes crazy trying to swat them with knives and frying pans. It's total chaos. Actually, the illustrations help make this even more climactic and exciting. Check them out in your book.
The suspense happens before the climax in this book, actually. Our narrator needs to figure out a way to get the Mouse-Maker into the witches' food. So he shuffles into the kitchen and needs to avoid getting caught. The entire time, we're wondering what's going to happen. How is he going to accomplish his mission and still make it out alive – especially when he accidentally gets caught in the pants of one of the cooks? Oops! Up until the very last second of the scene, we're holding our breath.
Once the climax has been reached and things have calmed down, we (and the characters) get a second to relax and reflect on what went down. Back at home, our narrator finds out from his grandma that witches are still out there. Even though they took out all the English witches, there will now be a new Grand High Witch and there are plenty of witches in other countries, too.
The narrator and Grandmamma hatch a plan to take out all the witches in the world: they will turn the new Grand High Witch and all her assistants into mice, then steal their records detailing where the other witches live, and travel the world doing the same to all the other witches. The two smarties head out on their way, eager to spend the rest of their lives saving the world. Heroic music should be playing in the background.