Sam Wood, a constant thorn in the Pilgrims' side, sent a 25-yard strike past Plymouth keeper Luke McCormick to make it 1-0 before the Chairboys' top scorer Morgan profited from hesitancy in the home defence to double that lead four minutes later.
Billy Knott sealed the victory in stoppage time with a superb chipped finish after chasing down a through ball.
The visitors offered little in front of goal although right-back Durrell Berry forced visiting goalkeeper Matt Ingram into action during a quiet afternoon.
Wood had signalled his intent with a fifth-minute shot that flew wide following a good cross from Marvin McCoy.
Defender Gary Doherty powered a near-post header just over McCormick's crossbar from a Wood corner from the right as the visitors looked the more likely side to score.
And so it proved as they registered a four-minute double salvo in the second-half, first through Wood, then courtesy of the in-form Morgan.
Gareth Ainsworth's side had scored two goals in each of their last four games but they would go one better this time thanks to Knott's late strike.