Not sure whether to tag this on the USA board or here.

We are taking a New England/Canada cruise in late September, beginning in Boston and ending in Quebec City. We will need to get back to Boston to catch our flight home - we are flying on special vouchers and cannot do an open-jaw itinerary - there are a few flights, but they are fairly expensive and not direct - they have pretty long layovers in Toronto. Is there no train or other mode of transport? I can't seem to figure out an easy way to do this.

I wonder if we'd be better off renting a car one-way, but not sure about the drop-off between two countries.

Anyone have any tips?

You can't take a Canada rental car into the US and leave it.
Best would be to take a ViaRail train to Montreal and then the Amtrak Adirondack train south all the way to New York-Penn station and then take a Northeast Regional train to Boston.
It is unfortunate that the Boston section of the Lake Shore Limited leaves Albany before the Adirondack gets there.
The other train option goes through Toronto, Niagara Falls and Buffalo and I don't think you want to do that.
If you could figure a way to get to Brunswick ME, Amtrak has a bus that connects to the Downeaster in Portland that gets you back to Boston.

I think you can take a bus from Quebec City to Montreal, and then a bus from Montreal to Boston. If your schedule permits, you can spend a night in Montreal, a great city.

Yikes, I think we are just going to suck it up and buy open-jaw tickets. The time and cost in trying to get back to Boston are just not worth it.

I guess that means we'll have to plan another vacation in order to use the airline vouchers we have.

Oh, darn.

I think we will be on the same cruise - NCL Sept 26th. We have the same problem. I called Alamo Rental car - we were so pleased with their service for us in Hawaii - and they said we could rent in Quebec City and leave the car in Boston - Quebec taxes are high so it will be about $200 per day - we thought of maybe driving to Montreal and Ottawa then to Boston. I was thrilled they said they could do it but thought the price was a little high so called Delta. Delta offered two flights 1) Quebec to Toronto to DETROIT to Boston leaving at 6:30 AM and arriving 2:30 for $834 per person! 2) Quebec City to NY JFK to Boston leaving at 2:30 and arriving at 11:30 for $1,150 per person - both economy!!!! That made the rental car look like a real bargain. I use a transport chair so would prefer to drive and enjoy the scenery so I will be calling Alamo Monday to book the car. Let me know here what you decide.