Substitute Luke Daley's first touch of the ball was to tee himself up for a superb strike from the right that bounced off the base of the far post.
Daggers goalkeeper Jon Bond made a great save during the ensuing goalmouth scramble before the ball eventually fell out to recalled Plymouth left-back Robbie Williams, whose 75th minute left-foot strike from outside the box beat Bond before the woodwork intervened again.
Argyle were left to rue a host of missed first-half opportunities. Striker Nick Chadwick fired over in the ninth minute after great work down the right from full-back Paul Bignot.
On-loan Burnley striker Alex MacDonald was bundled off the ball by central defender Mark Arber as he shot wide from 10 yards in the 20th minute.
Just before half-time midfielder Conor Hourihane fired over when it looked easier to score from MacDonald's superb reverse pass after the tricky striker had beaten three defenders on his way to the byline.
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