Not particularly difficult, given the quality of most television writing out there. To be fair, it is very different to establish a complex story, and to resolve it all within 47 minutes.
If the screenwriter leaves too much out, then you have the "Agatha Christie" problem, where there is no textual support for the solution until the deus ex machina revealed in final pages. If the screenwriter puts too much in, then the story becomes a dull, linear story.
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--James