The Harvard University campus seen in the movie wasn't actually Harvard but in fact McGill University in the province of Quebec in Canada.
The road signage in Montreal in Québec, Canada caused an unexpected problem for the production according to an article published in the 12th September 1979 edition of show-business trade-paper 'Variety'. Until 1977, the city's street signs had only been in English but new laws introduced that year meant they needed to also be in French. The problem with this was that filming in Montreal was also doubling for Boston which is located in the USA and has only English street signage.
The movie's MacGuffin was a rare valuable 18th century document that could expose America's first president George Washington as a traitor.
The film was made and released about two to three years after its source novel "The Glendower Legacy" by Thomas Gifford had been first published in 1978.
TV Guide described this motion picture as a "Canadian tax-shelter production".