The past perfect tense is used when expressing activity that was completed in the past before another past activity or time:

–Until yesterday, they had never seen the film.

–After the restaurant had closed, the customers went home.

To form the past perfect, use had + the past participle.

Examples of Past Perfect

• Yes, we became friends almost twenty years ago. She had moved here from Washington.
• They had never seen my apartment until last week.
• We called him after we had gone to the store.