For 22 years, every summer evening was marked by an event in Portland Harbor: The departure of the Scotia Prince, steaming for Yarmouth, Nova Scotia.

It was as regular as the tides, and for the people who watched the ship from the Eastern Prom or the Casco Bay Islands, it was a shock when the event suddenly stopped happening in 2004.

A high-speed ferry, The Cat, took its place from 2006 to 2009, until the provincial government of Nova Scotia dropped its subsidy, and that service also disappeared.

But now Portland looks like it will once again be served by a daily car ferry that would steam out of the harbor for an all-night trip to Canada between May 31 and Oct. 1.

Nova Scotia has selected a Maine firm, Quest Navigation, to run the service and has promised to provide $10.5 million for startup costs and $1.5 million a year for marketing over seven years.

They subsidize the service because Canada would be the prime beneficiary. The ferry will bring American tourists to Nova Scotia who might not have made the trip otherwise. The ferry carries car and driver 207 miles by sea, but the same trip is 750 miles over land.

But it is also a very good deal for Portland. If past patterns hold up, most of the passengers will be Americans from outside of Maine.

They will drive through the city, maybe stop to eat before they get on board and possibly stay for the night on their way home. Some will see Portland for the first time and see it from the water, its most attractive angle.

Along with the container ship service conducted by Eimskip, the Icelandic steamship company, the new ferry (which would be called the Nova Star) will add to commercial activity in the harbor, generating interest in the Portland waterfront.

The return of an international ferry could not happen without significant support from the state. The $20 million Ocean Gateway terminal, built for but never used by the Scotia Prince, was financed by the city and state. When Nova Scotia was deciding whether to move forward, Gov. LePage met with provincial officials and offered to assist with the marketing.

There are still some details that will have to be worked out before the deal is finalized, but we are much closer to the return of overnight car ferries to Canada than we have been in the last nine years.

This is a good deal for Canada and a good deal for Maine. The revival of ferry service as soon as next spring would be something to celebrate on both sides of the border.