Luton send Plymouth crashing
Rossi Jarvis (15) put the stricken home side ahead and after Argyle thought they had equalised, Tristan Plummer scored 13 minutes from time to seal a morale-boosting win.
Irish international left-back Damien Delaney proved to be the matchwinner for QPR as the wealthy Championship side beat League One Swindon 3-2 after extra time.