Sometimes it is observed that two actions had taken place in the past, one after the other. In such cases, Past Perfect Tense is used for the action that had happened earlier and Past Indefinite Tense is used for the other part of the sentence.
Generally, confusion often arises about which part of the sentence should be placed first and which one should be placed afterwards. You can put in either way; however, in such cases the following the golden rule should be kept in mind:
‘If you want to put the past perfect tense in the beginning, combine the two sentences with' before', and if want to put the past perfect tense afterwards, combine them with ‘after'.
I think the following two examples will clarify the matter.
•The doctor had come before the patient died.
In this case, the doctor had already arrived before the death of the patient. Therefore, the portion reporting the arrival of the doctor is placed in the Past Perfect Tense. The death of the patient took place after the arrival of the doctor. Therefore, this portion is placed in the Past Indefinite Tense. Since we have put the Past Perfect Tense earlier, we have combined the sentences with ‘before'.
Now look at the following sentence.
•The patient died after the doctor had come.
Here also, two things happened; the doctor arrived and the patient died. But here, we have put the death of the patient in the beginning and the arrival of the doctor afterwards. Therefore, we have combined the two sentences with ‘before'
The sense of both the above sentences is same only we have put them in different ways.
As shown above.