The Past Perfect Tense refers to a time earlier than before now. It is used to make it clear that one event happened before another in the past. It does not matter which event is mentioned first - the tense makes it clear which one happened first.

'Just' is used with the past perfect to refer to an event that was only a short time earlier than before now, e.g.

The young woman had just led her grandma before she had to go away.

They had never met in life before this evening.

The ceremony of graduation had just finished before the rain started.

The grandfather had just made his kiddo laugh until he had to go to school.

They hadn't decided it before he went away.

I had told it to him before he started ignoring me.

She had finished reading W. Scott before started reading W. Shakespeare.