A story of a guy who was supposed to pick his parents on time at the airport but he left late.
I finally finished tidying about 3 a.m. and a few minutes later I was fast asleep. I woke up suddenly at 8 a.m. I had arranged to meet my parents at the airport at 8.30 a.m. but I hadn't set the alarm!
I quickly set off for Heathrow airport, but it's one of the biggest airports in the world! I had no idea which terminal they (arrived/had arrived) at!
The last narrative event is had (I don't think it is the setting off), so it is the RT (reference time). At this point of time he brings their past arrival event to represent his current state of not knowing where they are. This interpretation/inference is supported by describing Heathrow as one of the biggest airports in the world which makes it difficult to quickly know where they are.
Before yesterday, which was just a few hours ago!, the criteria of choosing arrived or had arrived wasn't narrative/cutaway perfect way of thinking. Instead it was based on more or less an order of events! What a shame!
Am I right? To all and esp. to @StoneyB because I claim to be his student!
Update: I forgot to state that the chosen form is had arrived. I haven't slept yet and it's almost dawn!