Motherwell struck early through Chris Long but were stunned by a dominant second half Hamilton Accies display as the visitors won 2-1 at Fir Park on Sunday.
Despite the defeat, Motherwell remain third in the Scottish Premiership going into the winter break, eight places and 19 points above Accies.
Motherwell threatened in the very first minute when Chris Long's initial shot was blocked and Liam Polworth's effort from the follow-up was deflected narrowly wide.
But play soon raged to the other end a cross from the left found Accies striker George Oakley whose attempt was thwarted before the rebound was sent weakly at keeper Mark Gillespie by Accies' David Moyo.
The Steelmen then hit the front in the fifth minute when Long shot home superbly from distance with his right foot.
There was a rousing minute's applause in memory of Motherwell great Phil O'Donnell in the 10th minute - on the 12th anniversary of his tragic death after collapsing on the pitch in a home league game against Dundee United.
On 17 minutes a fine move between Motherwell's Grimshaw, Long and Polworth ended with the latter's shot being comfortably held by away keeper Luke Southwood.
Almost immediately there was another opportunity for the hosts when James Scott nodded a through ball onto Long who shot wide.
Accies had a decent effort on 27 minutes when Mickel Miller shot powerfully but too straight at Gillespie after a long free-kick from the right had been partially headed clear by the home defence.
Motherwell then survived a scare when Miller sent a poor free-kick effort wide after Mugabi had fouled Scott Martin on the edge of the box.
Accies were coming more into the game but Motherwell created another opening when Scott's cross from the left was flicked wide by the head of Hylton.
The final action of the half saw Scott shoot wildly over.
Accies came out determined at the start of the second half and pressurised the Motherwell goal, with Miller sending two attempts off target.
Motherwell tried to get back into it and O'Hara sent a dipping free-kick wide.
But Accies were soon back on the rampage and a brilliant long range shot by Moyo was tipped over by Gillespie.
A long ball through the middle then put Gillespie and Mugabi under pressure from Miller but the hosts survived as Mugabi mopped up the danger.
Motherwell were not at the races in the second half and Accies created yet another chance when Aaron McGowan's cross was nodded wide by Moyo.
Accies deservedly levelled on 67 minutes when McGowan's right foot shot from the edge of the box was deflected into the net past Gillespie.
Martin then burst forward for the visitors and sent a long ranger not too far off target.
Accies then stunned Fir Park in the 77th minute when a long cross from the right was headed home by Moyo.
Motherwell failed to create any scoring chances in the latter stages and although it was a disappointing day, the Steelmen still end 2019 in the Scottish Premiership's top three.
Motherwell: Gillespie, Carroll, Grimshaw, Campbell, Long, Hylton (Seedorf 64), Scott (Hartley 64), Polworth (MacIver 79), Mugabi, Gallagher, O'Hara.
Referee: John Beaton