It has significance as a unit, and a thread can be traced all the way along. Plot, on the other hand, is an item that occurs within that story. So for example, there are twists and turns in the story caused by these episodes, or plots, that crop up. They are each of lesser importance in themselves, but they all contribute to the work as a whole, creating interest and sometimes also contrast. The plot element of the balloon scene is an example of a little excursus from the main story and some of the places that Dorothy visits are also branches of sub plot . The scene where the wizard tells Dorothy to find the broom is an example of a new plot being inserted into the story and this, too, diverts her from her main goal of returning to Kansas for a while. It motivates her to take a certain course of action and increases an element of danger because she has to encounter the wicked witch.
The film begins with Dorothy out walking with her dog when suddenly a tornado arrives and all the Kansas characters are depicted rushing to find shelter. This dramatic start creates suspense, because Dorothy runs here and there, flinging her arms out and wrestling with items in her desperation to find a safe spot. The whole scene is filmed in black and white, and it shows a rather plain and drab country atmosphere with chickens and horses. There is some cartoon-like camera work when Dorothy gets hit on the head and lies down in bed watching figure pass by through the window, as if being whirled up in the tornado. Finally the camera pulls right away and there is an image of the house spiralling up and away. Suspense is created at this point because the viewer wants to know what happens to Dorothy and Toto.
In the final scene there is a repetition of the spiralling house but this time it spins downwards, in reversal of the opening sequence.