St Mirren staged a wonderful comeback to sink Motherwell at Fir Park but defeat for Dunfermline means both sides will stay in the Premier League.
St Mirren celebrate a wonderful comeback at Fir Park
A Ross McCormack diving header was the highlight of a dire first half.
Well's McCormack then tucked in a penalty early in the second half before the Buddies came roaring back.
Goalkeeper Colin Meldrum let a John Sutton header through his legs before Billy Mehmet levelled with a cool shot and Sutton cracked in a late volley.
Motherwell manager Maurice Malpas made seven changes following Monday night's thrashing at Dunfermline.
Meldrum returned, while their were recalls for Willie Kinniburgh, Marc Fitzpatrick, Steven McGarry, Paul Keegan, Kevin McBride and McCormack.
The visitors were unchanged after their good win at Tannadice last weekend.
A nervous start saw both sides making a number of mistakes, with passes regularly going astray.
Motherwell were first to threaten when a Krisztian Vadocz shot was headed clear by John Potter and McGarry almost got on the end of McBride's cross before goalkeeper Chris Smith took control.
The visitors were struggling to make any attacking impact and Stewart Kean's shot on the turn from a difficult angle that flashed wide was the closest Saints came in a dismal first half.
Seven minutes short of the interval, the home side went ahead when McCormack grabbed his first SPL goal for the club.
The former Rangers striker flew in to head home after McBride had nodded Keegan's cross into the six-yard box.
McCormack bagged his second goal of the afternoon with a penalty early in the second half.
Veteran defender Andy Millen was penalised for a foolish handball and the Well forward smashed his spot-kick past Smith.
The Buddies responded by throwing on strikers Sutton and Mehmet and both substitutes found the net within four minutes of their arrival.
Sutton's weak header from an Alan Reid cross somehow slipped through Meldrum's fingers and his legs.
And Mehmet levelled with a composed finish after latching on to a long throw-in from Kirk Broadfoot.
McCormack came close to his hat-trick with a delightful lob but Smith scrambled back to tip the ball over the crossbar.
The lively Well striker then saw his fierce rising strike pushed away by the St Mirren keeper and later flashed another shot narrowly wide.
As play raged on at a rapid rate of knot, Sutton hit crossbar before blazing a great volley high into the net on 83 minutes to seal a memorable win.
Motherwell: Meldrum, Corrigan, Craigan, Kinniburgh, Quinn, McBride, Fitzpatrick, Vadocz, McGarry (McLean 63), McCormack, Keegan (Clarkson 79). Subs Not Used: Graeme Smith, Kerr, Darren Smith, Connolly, Jamie Murphy.
Booked: Quinn, Corrigan.
Goals: McCormack 38, 49 pen.
St Mirren: Smith, van Zanten, Potter, Broadfoot, Maxwell, Corcoran, Murray, Millen (Sutton 54), Reid, Kean, Burke (Mehmet 54). Subs Not Used: Hinchcliffe, Brady, Mackay, McKenna, McGinn.
Goals: Sutton 56, Mehmet 59, Sutton 84.
Ref: M Tumilty