We use The Past Perfect Tense to express a past action that occurred either before another activity or before a point of time in the past.
Forming Past Perfect Tense
Affirmative Form
Subject + had + verb3 + complement
He had left the office
Negative Form
Subject + hadn't + verb3 + complement
He hadn't left the office.
Question Form
Had + subject + verb + complement ?
Had he left the office?
Negative Question
Hadn't + subject + verb3 + complement ?
Hadn't he left the office?
Past perfect tense
We form the past perfect tense with had and the past participle of the main verb.
If we conjugate the verb 'to go' as an example in the past perfect tense we're going to have :
Subject + had + gone ( past participle of 'to go' )
I had gone We had gone
You had gone You had gone
He had gone They had gone
She had gone
It had gone
When do we use the past perfect tense ??
We use the past perfect tense to describe an action that took place in the past before another past action.
Examples
By the time we arrived , they had gone.
She said that she had seen that movie.
His customers had waited outside until Mark came to the shop.
Customers were already outside when Mark arrived to the shop. Act of waiting occurred before Mark's arrival.
The train had just left when I got to the station.
The train left and a few minutes later I got to the station.
Hint:
Use the Past Perfect Tense after 'AFTER'
Use the Past Perfect Tense before 'BEFORE'
She had cooked dinner before I got home.
I got home after she had cooked dinner.