Follow up reply to my question posted last month:

We rented from Europcar (pick-up in Tours but return at Montparnasse). Fortunately, my parents were at Gare Montparnasse a few days earlier and they made some inquiries for me as to where the drop-off place is.

It turns out that Europcar (and a few other rental car companies) drop-off is in the parking garage of Hotel Meridien, next to the train station. The level is -4.

I would have never figured it out if my parents didn't check for me.

I would never rent a car and plan to drop it off somewhere without specific address and directions to the drop off point. That goes for Kansas City as well as for Paris.

We dropped a car once at Montparnasse and picked up one there another time. Both were easy as could be, but we had the driving directions all printed out in advance. Once you have the address, the print out of directions is easy. Frankly I've had much worse times at poorly marked US airports dropping off cars.

Thank you so much for your tip yk about dropping off a Europcar rental at Montparnasse. We'll be dropping our car off there in March, and your tip is sure to save us alot of frustration!