Scotland struck two minutes before half-time to leave Argyle still looking for their first win of the season.
It might have been so different if referee Andy D'Urso had not ruled out what looked like a perfectly good goal by Pilgrims centre-back Marcel Seip early in the second half.
However, the visitors deserved their victory against a lucklustre home side, who, much to the delight of the visiting supporters, contained four players with Cardiff City links as well as ex-Swan Rory Fallon.
One former Bluebird, striker Steve MacLean, replaced Jamie Mackie in an otherwise unchanged Argyle line-up, while Swansea recalled Angel Rangel for Matt Collins.
Swansea kept Argyle penned in their own half for most of the first half, with Darren Pratley and Ferrie Bodde bringing the best out of man-of-the-match goalkeeper Graham Stack.
However, it was not until half-time approached that the visitors edged in front, Scotland exchanging passes with Pratley before sliding the ball past Stack.
Argyle were deprived of a goal when D'Urso's baffling decision denied Seip of a second successive home strike after he headed home Luke Summerfield's left-wing corner early in the second half.
There was no appeal from any Swansea player and countless television replays failed to show D'Urso's post-match contention that Swans goalkeeper Dorus de Vries had been impeded.
Thereafter, Swansea never looked threatened and made fairly light work of hanging on to their lead to register a second Championship victory since their promotion last season.