The creator of Community and Rick and Morty describes how he breaks down episodes of his TV shows.
This short video describes the eight major story beats the focus character of the episode goes through, starting out in the 'normal world', having a need/desire that they find a way to satisfy, then having to deal with the (often unforeseen and unintended) ramifications of this before ending up back where they began, but now a little bit different.
It's reminiscent of the classic Hero's Journey model, if a little tweaked and focussed down for the half-hour TV format. The video is only three minutes and worth a watch. It also shows how the same eight-beat formula fits into the example episode's B-story in the same way.
If you're having trouble figuring out the plot for your great idea, using Dan Harmon's Story Circle could be a helpful exercise.