Tom Eaves struck a hat-trick as Plymouth's faint play-off hopes were well and truly extinguished after a resounding 5-2 defeat at Gillingham.Argyle not only needed to win but also required sixth-placed Charlton to lose - and for there to be a six-goal swing in proceedings.Plymouth, who were in relegation trouble back in November, could not live with Steve Lovell's side and especially giant striker Eaves.He struck a 21-minute hat-trick either side of the break to ensure Argyle will be playing in the third-tier next season.Josh Parker's strike gave Gillingham an early lead before Anthony Grant bundled in an equaliser for the visitors.But that was as good as it got for Derek Adams' side.Eaves then stole the show, first capitalising on a slip from a defender and slotting home before finishing coolly to make it 3-1.The giant striker followed up that feat to complete his second treble of the season with a header.Graham Carey's header reduced the arrears for Argyle but sub Elliott List had the final say with a tight finish in stoppage time.