A penalty deep into injury-time by Argyle captain Paul Wotton - his fourth goal of the season - ensured the Pilgrims had the last word in a game of wildly contrasting fortunes at Home Park.
Forest boss Joe Kinnear was absent due to a family illness and missed seeing Argyle's David Norris and Graham Coughlan give the home side a comfortable first-half lead before a double by Eoin Jess, the late second while Plymouth's players were still appealing for a penalty, levelled matters.
Forest's rookie third-choice goalkeeper Barry Roche was held blameworthy for at least two goals in the Reds' 4-1 defeat by Coventry at the weekend, and he was certainly at fault for the opener at Home Park.
He failed to read Norris' intention as he turned sharply in the penalty area and was unable to react to a sharp shot that was no more than a yard to his side when it went past him.
If injury-hit Forest really wanted to point fingers, they could equally have been directed at Marlon King after Andy Reid, who has spent much of the summer anticipating an apparently forlorn move to Spurs before Tuesday's transfer deadline, created the opportunity.
He beat two men on the left flank and crossed perfectly for King who, unmarked, should have done better than to head weakly straight into the arms of grateful goalkeeper Luke McCormick.
The Pilgrims doubled the margin thanks to Coughlan's bravery. The Dublin-born centre-back stooped at the far post and took a boot in the face as he headed home David Friio's flicked header from Wotton's rapid inswinging corner.
However, Forest immediately fired themselves back into contention – and a warning shot across the good ship Pilgrim's bows - when Jess volleyed home superbly from 25 yards after Argyle had failed to clear Irish international Reid's right-wing free-kick.
With ten minutes left, Friio appeared to have been fouled by the otherwise impressive Wes Morgan in the penalty area, but referee Ray Olivier gave Forest a considerable benefit of the doubt and, while Argyle were still arguing the toss, Johnson broke to set up Jess for his second of the night.
There was still time for Argyle to fight back, and, when Chris Doig tripped substitute Keith Lasley in the box in the third of four minutes of stoppage time, centre-back Wotton obliged.