Two late goals from Grant Brebner capped a remarkable comeback from Dundee United at Fir Park.
Grant Brebner celebrates his late winner
United found themselves 2-0 down early on after goals from Alan McCormack and Scott McDonald, before Lee Miller headed in a lifeline.
Well's Marc Fitzpatrick and Jim Hamilton and United's David Fernandez and Miller all netted after the break.
The outcome of this game became impossible to predict until Brebner struck twice in three minutes.
Motherwell fired out the early warning signs when McDonald surged into the box only to glance his header just wide.
However, the United defence were not quite so fortunate in the sixth minute, when McDonald set up on-loan midfielder McCormack to head his first goal for Motherwell from six yards.
United barely had time to catch their breath before Motherwell were slicing open their defence again.
Jim Paterson fired a dangerous ball into the box but Hamilton headed harmlessly wide.
Paterson was involved again as Well went two up in the 12th minute.
The former United midfielder's shot was cleared off the line by Brebner but goalkeeper Derek Stillie was still recovering from the initial shot when McDonald pounced on the rebound to squeeze the ball under his body.
The Terrors were being terrorised and they should have been three behind when McDonald squared into the path of Hamilton, but he missed the ball completely from a yard out.
Instead of killing the game off, Motherwell allowed Dundee United to mount a fightback.
Miller showed why he had been courted by both Hearts and Aberdeen over the summer when he bulleted a header past Meldrum from 12 yards, three minutes before the break.
The second half was just three minutes old when David Keogh's cross was nodded into
the path of fellow substitute Mark Fitzpatrick and he stabbed home from just outside the six-yard box.
Their joy was short-lived as United pulled a goal back in the 53rd minute, when Crawford knocked the ball into the path of Fernandez and the Spanish hitman drove home.
Motherwell were determined not to allow United to snatch anything from the game and, three minutes later, Hamilton headed home Steven Hammell's pinpoint free-kick.
The goals continued to come with Mark Wilson setting up Miller to head his second of the day in the 67th minute.
United then had their noses in front against all the odds when Brebner grabbed two quick goals.
The first came in the 71st minute when substitute Collin Samuel squeezed the tightest of passes into the path of the United skipper, who tapped home from less than a yard.
His second, three minutes later, was another simple finish after brilliant build-up play from Miller.
Motherwell: Meldrum, Paul Quinn, Craigan,
Kinniburgh (Fitzpatrick 45), Hammell, Kerr, McCormack,
O'Donnell, Paterson (Keogh 45), McDonald, Hamilton,
Fitzpatrick (Andy Smith 80).
Subs Not Used: Graeme Smith, Clarkson, Fagan, Darren Lee Smith.
Booked: Paul Quinn, Kerr.
Goals: McCormack 6, McDonald 12, Fitzpatrick 49, Hamilton 57.
Dundee Utd: Stillie, Wilson, McCracken, Archibald, Duff, Kerr,
Brebner, Robson (Samuel 61), Miller, Crawford (McIntyre 67),
Subs Not Used: Samson, Dodds, Kenneth, Robertson, Cameron.
Booked: McCracken, Brebner.
Goals: Miller 42, Fernandez 53, Miller 67, Brebner 71, 74.
Ref: M Ritchie