I have found these two sentences where past perfect seems to be obligatory. I was just wondering if past simple can work too. Here are the examples:
I had set my alarm before I went to bed, but for some reason it didn't go off in the morning.
Ethan had forgotten to turn off the tap before he ran to answer the door, and so, eventually, the house flooded.
In both sentences the verbs in past perfect are the causes so it is obvious that it comes before. The sequence of events is very clear.
The house flooded because Ethan forgot to turn off the tap before he ran to answer to the door. And the writer complaints the alarm did not go off even though he set it before going to bed.
So in this case can we deduce that past prefect is only used for emphasizing the clause? What is the reason of using it if the sequence of events is clear?