Study this example situation:
Sarah and Paul went to the same party last week, but they
didn’t see each other. Paul left the party at 10.30 and Sarah
arrived at 11 o’clock.
So when Sarah arrived at the party, Paul wasn’t there.
He had gone home.
had gone is the past perfect

The past perfect (simple) is had + past participle (gone/seen/finished etc.).
Sometimes we talk about something that happened in the past:
- Sarah arrived at the party.
This is the starting point of the story. Then, if we want to talk about things that happened before this time,
we use the past perfect (had …):
- When Sarah arrived at the party, Paul had already gone home.
Some more examples:
- When we got home last night, we found that somebody had broken into the flat.
- Karen didn’t come to the cinema with us. She’d already seen the movie.
- At first I thought I’d done the right thing, but I soon realised that I’d made a big mistake.
- The people sitting next to me on the plane were nervous. They hadn’t flown before. or They’d never flown before
Compare present perfect (have seen etc.) and past perfect (had seen etc.):

Compare past simple (left , was etc.) and past perfect (had left , had been etc.):
