This was a romantic tale speared by a twisted knife. Joe Cole had done all that he could to steal everybody's hearts all over again. He looked like being the game's catalyst, as he helped his team to recover from a goal deficit by creating two assists that James Collins finished off gleefully.
Yet just as West Ham and Cole were reaquainting their relationship in the sweetest way possible, Robin van Persie arrived to throw a metaphorical bucket of chilled water all over the cosy claret and blue embrace. A stoppage-time equaliser from the substitute spared United embarrassment, and kept up the trail of electrifying comebacks. After a topsy turvy and compelling game, United and West Ham will meet again at Old Trafford.
Regardless of the result, there was always going to be a fairytale element to the occasion with the sight of Cole trotting on to the pitch. The roar as the favourite son's name and number boomed over the tannoy was as hearty as they come.
The 31-year-old lined up in wide midfield. Although he looked understandably low on match fitness, his appetite was cranked up. He looked so eager to feel the sense of boot on ball, to spot a pass.
The visitors were naturally oblivious to the home crowd's sentiment. Although Alex Ferguson tinkered with more than half of this team compared to the starting XI which swatted Wigan aside, it was still a United selection strong on experience and quality. They forged an early opening of real promise, when Paul Scholes picked out Chris Smalling with a sublime pass. The defender loped into the box to tuck over a cross that just evaded Javier Hernandez.
West Ham responded and won a corner. Sam Allardyce jiggled around on the bench. He was psyched, expectant. One imagines there had been a fair amount of aerial practice this week at Chadwell Heath. Alou Diarra's leap required both Scholes, and then Nemanja Vidic, to repel the threat on the goal line.
Before long, it was Dan Potts with the clearance, when Vidic thumped a corner goalwards. It was a big moment for the teenager, who recently returned from a loan spell at Colchester.
United profited from slicker means. In the 23rd minute, Hernandez broke down the right and whipped in a cross that careered all the way to Tom Cleverley, who arrived from his station on the left to beat Jussi Jaaskelainen with panache. He exhibited sweet technique to curve his shot, with perfect placement, inside the far post.
The lead proved to be shortlived, though, as West Ham came bouncing back. Cole was the provider, receiving the ball from Ricardo Vaz Te, turning, looking up, and sending in a lofted cross that was gobbled up by Collins.
United picked up after the break, perkier and more dominant in possession. But they were a little careless, with Danny Welbeck and Cleverley lacking ruthlessness from interesting positions.
West Ham turned the tide. Danger brewed as David de Gea theatrically caught a Carlton Cole header. Then cometh the hour, cometh a replica of West Ham's first. Joe Cole again found that moment of clarity to launch a searching ball into the penalty area. There was Collins, again, to glance in a header even De Gea couldn't get close to.
Time to get serious. Ferguson sent on Robin van Persie and Antonio Valencia. United's top scorer was soon involved, working the ball out to Alexander Buttner, whose cross fell for Welbeck. The England striker scooped a close-range header over the bar.
The home crowd saw four minutes of additional time go up on the clock and gave out a collective groan. If they sensed that something was coming, they were right. Van Persie was freed, accelerating down the right channel with devastating precision and steering with typical expertise past Jaaskelainen.