Kettering shrugged off the dismissal of Jerel Ifil to hit back for a draw at win-shy Alfreton.
Midfielder Anton Brown headed Josh Law's free-kick into the bottom corner before Ifil was shown a straight red card for a professional foul on Law.
Adam Cunnington was denied an equaliser when his header was superbly saved by Alfreton goalkeeper Joe Day.
But Cunnington was not to be denied, picking himself up after being fouled by Theo Streete to convert the penalty.
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Alfreton Town manager Nicky Law told BBC Radio Derby:
"It was a game we should have won. We bossed the game in the first half.
"In the second half, it's always difficult against 10 men but we didn't have enough players who wanted to get on the ball and take responsibility.
"They did better with 10 than they did with 11."
Kettering Town manager Mark Stimson told BBC Radio Northampton:
"First half it wasn't happening for us. We conceded a goal and had a man sent off so at half-time we had to re-shape and went positive.
"Fair play to the boys; they dug in and they've put a shift in.
"It was great for the supporters to go home with something tonight thinking at least they are playing for their shirt now and they are giving everything."