Bruno Fernandes' superb 78th-minute free-kick gave Manchester United victory in a thrilling FA Cup tie with old rivals Liverpool at Old Trafford.
Liverpool led a fantastic contest through Mohamed Salah, who then equalised after Mason Greenwood and Marcus Rashford had struck for the hosts either side of the break.
But in a game which had everything last week's drab stalemate between this pair at Anfield lacked, Fernandes came off the bench to have the final word after Fabinho had fouled Edinson Cavani on the edge of the area.
Fernandes might have been slightly off the pace in recent games but when Ole Gunnar Solskjaer needed his £47m inspiration to come up with another special moment, the Portuguese delivered, bending his shot round the wall and beyond Allison's reach.
The victory earns United a home meeting with an in-form West Ham side managed by former boss David Moyes in the fifth round.
But the search for form goes on for Liverpool, whose only win in seven games since that seven-goal hammering of Crystal Palace came against Aston Villa's kids in the last round, and who have a meeting with Jose Mourinho's Tottenham looming on Thursday.
Meanwhile Leicester City had to come from behind to avoid an FA Cup upset at Championship promotion hopefuls Brentford.
But the Foxes were transformed after the break, equalising 49 seconds after the restart as James Maddison fed Cengiz Under for a sweeping finish.
Five minutes later, Youri Tielemans was tripped in the box and converted the resulting penalty, while Maddison deservedly got on the scoresheet by following in a rebound.
Elsewhere Jay Rodriguez's double and a Kevin Long tap-in secured Burnley's progress to the fifth round of the FA Cup with a comfortable win over struggling Fulham.
The Clarets produced a dominant display and went ahead when Rodriguez headed home Jack Cork's cross on 31 minutes.
Rodriguez doubled their lead with a penalty after Matej Vydra was bowled over in the box, ending a 19-game goal drought.
Long netted Burnley's third as he poked home 10 minutes later.
Burnley will face Bournemouth or Crawley Town in the fifth round - the Cherries host Crawley on Tuesday, 26 January.