Concord hit the woodwork twice and had a shot cleared off the line in the early going but suffered a severe blow when striker Leon McKenzie was sent off before the half-hour mark.
They still managed to take a 70th-minute lead through Ben Greenhalgh and held it until three minutes before the end of normal time, when substitute Esmond James grabbed the equaliser from a corner.
The turnaround was complete two minutes into added time when Tom Pett (pictured) netted the winner. Stones are now eight points behind leaders Whitehawk with three games in hand, while Concord are a further point back and have played a game more.
Waltham Abbey at last began the final third of their Ryman North programme, chalking up a 2-0 home win over Needham Market. They have another 13 games to play.
Louis Bristow put them ahead in the 53rd minute and Dean Green added the second with 20 minutes left.
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