Mackail-Smith 63, 69
AND so it ends.
A tortuous Championship season finished in glum fashion with bottom-club Peterborough securing a rare victory against an Argyle side they will face in League One next year.
Bradley Wright-Phillips scored a terrific opener for the Greens in the first-half and three points seemed a formality until Craig Mackail-Smith stunned Home Park with two goals in the space of six minutes after the break.
Argyle head coach Paul Mariner drafted in goalkeeper Romain Larrieu for his first appearance since January after David Stockdale returned to Fulham following his successful loan spell at Home Park.
Kári Árnason switched from midfield to defence with Réda Johnson still suffering from a groin problem picked up in the 3-0 defeat at Nottingham Forest last weekend, and Karl Duguid came in at right-back as a late replacement for Richard Eckersley.
Chris Clark slotted into the vacated spot in midfield alongside newly-crowned Player of the Season Carl Fletcher, while winner of the Young Player award, Joe Mason, started in attack with Wright-Phillips.
The unfamiliar names on the Argyle bench were youth-teamers Ollie Chenoweth and Curtis Nelson. Goalkeeper Chenoweth is a second-year apprentice from Cornwall and defender Nelson from Staffordshire.
Peterborough manager Gary Johnson made two changes from the 1-0 home defeat to Ian Holloway's Blackpool last weekend. Joe Lewis returned in goal for James McKeown and Craig Morgan replaced Dominic Green in midfield.
It was a significant afternoon for Johnson, who left his role as Bristol City boss the day after succumbing to a 3-2 defeat at Home Park in March.
The first chance came from a tidy nod-down by Liam Dickinson and winger Tommy Rowe swept in from the left to drive a low volley narrowly wide.
Alan Judge was the first Green to show some bite with a nasty challenge on 18 minutes that seemed unsuited to the subdued atmosphere of the occasion.
Dickinson, who scored twice for Blackpool at the Theatre of Greens two season ago, remained the potent threat on display, and Argyle needed an astute challenge from Árnason to prevent him latching onto a clever cross by Mackail-Smith.
At the other end, the Pilgrims were clearly missing the defence-stretching runs of Jamie Mackie, who has missed the last two games of the campaign with a calf problem.
Dickinson did finally lift the tempo with a terrific finish from a quick free-kick, but he was denied a final day goal by the assistant referee's flag. Within a minute, the same man headed wide from a drifting cross by Charlie Lee.
It took more than 30 minutes for the Greens to wake up, and when they did Judge threaded a pass into the box for Bondz N'Gala, who had stayed forward following a corner. The big defender pirouetted beautifully to manufacture enough space for a poked effort against the post.
Argyle then took the lead through Wright-Phillips, who scampered on to a long pass down the left channel by Clark and finished delightfully with a low half-volley across Lewis.
The Pilgrims should have then doubled their lead when Wright-Phillips bamboozled Lee by the corner flag and squared for Mason, who wrong-footed Lewis with an effort that slipped a fraction wide.
The half ended with Fletcher lofting a pass forward for Wright-Phillips, who controlled the ball exquisitely before fizzing an instant shot inches beyond the far post.
Chris Barker replaced Onismor Bhasera at half-time in a straight switch at left-back as Argyle continued their strong finish to the first period with Judge marauding through the Posh midfield at will.
Peterborough's principal threat remained Dickinson and he turned sharply to meet a Josh Simpson flick, but the eventual shot was easy for Larrieu. N'Gala was next to thwart with a brave challenge at the near post to deny the big striker.
As the sun began to twinkle through the blustery conditions, the pattern and pace of the second-half suggested both sides were now thinking about summer on the beach.
Out of nowhere, Peterborough equalised. Mark Little found space on the right to drive over a low cross that deflected perfectly for Mackail-Smith to slot home from close range. It was simple as it sounds.
Clark's season ended with a bruising clash that left him holding his face in agony and Mariner swiftly promptly introduced Yala Bolasie for the battered Scot.
Mariner then had to fold his arms in dismay as Mackail-Smith gave Peterborough the lead. Once again it was all too simple with Tommy Rowe curling in a free-kick that the blond-haired forward glanced beyond Larrieu and inside the far post.
Peterborough were suddenly picking the Pilgrims to pieces and Larrieu needed a big left boot to stop Josh Simpson from adding a third with his poked effort.
Judge came within a lick of paint of rescuing the game with a sensational free-kick that thundered the underside of the bar, and Árnason could only scoop the rebound wide with the goal gaping.
in the final act of nine difficult months, Rory Fallon and Wright-Phillips had efforts cleared off the line in a sequence that seemed to sum up our campaign.
Have a good summer.
Argyle (4-4-2): 1 Romain Larrieu; 2 Karl Duguid (14 Rory Fallon 78), 11 Kari Arnason, 29 Bondz N'Gala, 35 Onismor Bhasera (15 Chris Barker h-t); 25 Alan Judge, 4 Carl Fletcher (capt), 7 Damien Johnson, 6 Chris Clark (36 Yala Bolasie 68); 10 Bradley Wright-Phillips, 32 Joe Mason. Substitutes (not used): 20 Luke Summerfield, 21 Ollie Chenoweth (gk), 22 Reda Johnson, 38 Curtis Nelson.
Peterborough (4-4-2): 1 Joe Lewis; 6 Charlie Lee, 24 Danny Andrew, 29 Ryan Bennett, 16 Mark Little; 31 Nathan Koranteng, 33 Josh Simpson, 4 Craig Morgan, 14 Tommy Rowe; 12 Craig Mackail-Smith, 7 Liam Dickinson (20 Ben Wright 64). Substitutes (not used): 13 James McKeown (gk), 25 Dominic Green, 26 Danny Mills, 27 Romone McCrae, 30 Scott Griffiths, 35 Carl Piergianni.
Booked: Andrew 39, Lee 48
Referee: Steve Tanner (Somerset).
Attendance: 8,557 (339 away).