Lupin on the Train

[Brooks R]

No: HPFGUIDX 238

I somewhat think that the situation was as follows: Lupin was on the 
train to get there (maybe he cannot apparate either, or if there was
a full moon recently, was too tired, as has been said); is certainly
too poor to afford a broom due to his difficulty holding a job; picked
that compartment of that car because he thought he was most likely to 
get some rest there.  Harry & Co. wound up in that compartment & that 
car for logical reasons (for one thing it makes the Slytherins have
to 
search the whole train, if they decide to drop in!). The fact that RL 
was there was useful for Harry & Co. both in terms of driving away
the 'Slytherin Slugs' AND when the Dementor came aboard, has much to
do 
with the fact that authors like to have good things happen sometimes 
(especially when they advance the plot).  But something Diane Duane 
suggested in her writing also comes to my mind- sometimes the 'Forces 
of Light' intervene in very subtle ways, arranging a good meeting or
a fortunate coincidence because they foresee that such events will be 
useful in the future and will help the people on the Light side to 
advanc and grow.  "There are no coincidences" - it happened that way 
because the Universe  (or the Forces of Light) *wanted* it to happen 
that way.