Alfreton Town had to settle for a 1-1 draw from their Blue Square Bet Premier encounter at the Impact Arena on Tuesday night.
It was the fourth time this season that the Reds had squandered an interval lead at home to end up sharing the spoils after Braintree Town, Kidderminster Harriers and AFC Telford United had been let off the hook in identical scenarios previously.
However it was deep into stoppage time before Law’s 27th minute opener was cancelled out, with Alfreton ending the game with ten men after Theo Streete had been sent off.
Striker Ben Tomlinson was unavailable for selection with a foot injury, but there was the opportunity for Anton Brown, Streete and Ross Killock to regain their positions in the starting line-up.
Paul Clayton glanced a header wide from a Josh Law corner in the sixth minute, then Cambridge responded with Tom Elliott firing over from a Michael Gash cross.
Visiting keeper Ross Craig did well to punch behind Law’s 19th minute corner at the back post as Darran Kempson homed in, then at the other end Elliott volleyed wide when put through by Andy Pugh.
Elliott then dragged the ball across the face of goal after a strong run in the 24th minute, but three minutes later Alfreton edged ahead when Law scored spectacularly from a free-kick after Clayton was fouled 20 yards out by Rory McAuley.
Reds’ keeper Jon Stewart pushed behind a better effort from Elliott within 30 seconds of the restart, then with three minutes of the first half remaining Dan Bradley fired wide after an effort from Matty Harriott had been blocked.
A stretching block by Kempson prevented James Jennings from equalising, then as the interval beckoned Brown’s diving header only just missed the target from a deep Law free-kick.
Controversy reigned on 53 minutes when Ross Jarvis saw his shot rebound off the post only for the referee to award a corner in the belief that Stewart had saved it, then when a subsequent flag-kick was awarded the frustrated keeper received a caution for kicking the ball away.
Nathan Arnold volleyed wide from the edge of the area after being teed up by Clayton in the 56th minute, then Harrison Dunk’s header drifted wide as United responded.
Clayton’s looping header from a Law cross also failed to trouble Craig, then on 72 minutes Law had to guide Robbie Wilmott’s chip away from the back post before Connor Franklin cleared Dunk’s follow-up off the line.
Stewart beat out Wilmott’s shot with nine minutes left on the clock, then the keeper held a curler from Gash from 25 yards, but Alfreton couldn’t quite see the game out and finally conceded in the third minute of injury time.
Dunk sprinted into the area rather too easily and was pulled back by Streete, who was dismissed as he was the last line of defence and had prevented a scoring opportunity.
Gash gave Stewart no chance from the penalty spot, and the keeper still had to pull off the save of the night to tip over Dunk’s shot as Cambridge sought a late winner.
ALFRETON: Stewart; Law, Kempson [Franks 76], Killock, Franklin, Bradley, Streete, Harriott, Brown, Clayton, Arnold.
Other subs: Denton, Meadows, Worsfold, Emerton.
Att: 534 .