Murdoch had played a ball to fine leg. Wicketkeeper Alfred Lyttelton ran around to field. The throw came in to Grace at point. Sammy Jones, who had completed his second run, nodded at Grace — by Australian accounts establishing 'a tacit understanding' that the play was over — then walked out of his crease and patted the pitch with his bat. Grace, with the ball still in his hand and the stumps in his sights, threw them down. The umpire had no choice. Jones was given out, run out for 6.
The gamesmanship was, strictly, within the laws. The ball had not been formally returned to the bowler; Jones had not 'made his ground' before being out of his crease. But contemporary cricketers — and most modern commentators — see it as the original act of letter-not-spirit cricket, the sort of thing that would now produce a televised tribunal.
Fred Spofforth was waiting to bat. By all accounts (Tom Horan's later writing is the primary source) he came out of the dressing room incandescent, and during the lunch break burst into the English changing room calling Grace a cheat. He is said to have told Murdoch, 'this will lose you the match.' By stumps Spofforth had taken 7 for 44 and Australia had won by 7 runs.
Whether Grace's run-out actually fired Spofforth's spell is impossible to prove. But the chronology and the eyewitness accounts are clear enough that almost every Ashes history connects the two events. The original Ashes was, in some sense, born from a piece of WG Grace gamesmanship that backfired catastrophically.