Here's why:
* Abstract nouns represent ideas, concepts, qualities, or states of being. They are not physical things you can touch.
* An episode is a distinct part of a larger story or series of events. It's not a tangible object, but rather a conceptual division of a narrative.
For example, you might say: "The latest episode of my favorite TV show was thrilling." You're not referring to a physical object, but rather a segment of a larger story.