Millwall paid a heavy price for their profligacy in front of goal as 10-man Exeter City came from behind to secure a share of the spoils with Adam Stansfield's late leveller.
Dave Martin's 21st-minute penalty had put The Lions firmly in the driving seat, and when Grecians defender Steve Tully was sent off early in the second-half, it should have been game over.
But instead of travelling back to London with three precious points in the bag, The Lions were caught out by a freak 88th-minute effort from sub Stansfield that looped beyond the reach of keeper David Forde and into the back of the net.
Having described Saturday's display against bottom club Wycombe as 'unexplainable and unacceptable', Lions boss Kenny Jackett had demanded a massive improvement from his players.
Jackett made two changes to his starting line-up with Andy Frampton replacing the injured Tony Craig and Martin coming in for Jason Price alongside Steve Morison and Chris Hackett in a three-pronged attack. Price dropped to the bench, where he was joined by fit-again Ali Fuseini following an eight game absence.
After a quiet start in which both teams tried to adapt to the blustery and wet conditions, The Lions began to start pushing forward with greater purpose and penetration, but it was Exeter who produced the first scoring opportunity on the quarter hour when Marcus Stewart flicked a header narrowly wide from six yards following a quick break down the left.
Visiting keeper Forde was called into action five minutes later with a comfortable stop from Ryan Harley's low grubber.
Play swung straight up the other end and when Martin broke into the opposing danger zone, Bertie Cozak stuck out a leg to send the Lions winger sprawling.
Referee Simon Hooper had no hesitation pointing to the spot - with Martin showing no hestitation as he lashed the ball past Andy Marriott with a text-book penalty to put Millwall 1-0 ahead.
With the wind at their backs The Lions tried to press on and force a second goal before the break.
Jimmy Abdou saw his 30th-minute drive deflected for a corner and then Danny Seabourne averted the danger with a timely tackle to dispossess Morison as he threatened to break clear.
Boss Jackett was forced to shuffle his playing pack at the start of the second-half with Alan Dunne replacing the injured Jack Smith.
Exeter had an early chance to put pressure on the visiting goal when Marc Laird was penalised for a foul on Scott Golbourne, but Harley's free-kick from the edge of the area fizzed over.
The home side found themselves not only a goal down, but a man down too when Tully was shown a yellow card for an ugly challenge on Frampton seven minutes after the restart. Having already been booked for an equally crude foul on goal-scorer Martin (13mins), referee Hooper had no option other than to send the Grecians defender from the field of play.
Millwall wasted a good chance to double their tally on 57 minutes when a great break involving Hackett and Laird set up Schofield in a decent position. Sadly the latter never seemed to get the ball totally under control and he was unable to find the precision final pass to pick out unmarked midfielder Laird, who had burst into the penalty area.
Exeter introduced Stansfield and Richard Logan 20 minutes from time in a bid to see if the duo - who both scored after coming on as substitutes at the weekend - could spark a change in fortunes.
Lions boss Jackett responded in kind by sending Jason Price on for Martin.
Shortly after, the visitors squandered a gilt-edged opportunity to double their tally.
A terrific run and delivery by Frampton found Morision, but the striker contrived to glance his 76th-minute header wide of the mark from five yards with the goal at his mercy.
Morison nearly made amends seconds later with a rasping left-foot shot that smacked the woodwork, and when Schofield tried to reach the loose ball, he was sent tumbling. To Millwall's fury referee Hooper pointed for a goal kick and not a penalty, which it surely was.
Boosted by their stroke of luck, Exeter began to play with a fresh impetus and it took a great goal-line clearance by Laird to avert the danger following Alex Russell's corner.
Forde then desperately claimed the ball at the second attempt from another dead ball delivery as Exeter sensed they could salvage something from the game.
And that is exactly what they did when, with just two minutes remaining, Stansfield's speculative cross caught the wind and flew in off the inside of the far post.
Thereafter it was the home side who played with greater urgency, and an uncomfortable three minutes of injury-time could not finish quick enough for The Lions, who by the final whistle were on the back-foot trying to stem the tide of Exeter attacks.
Exeter City: Andy Marriott, Steve Tully, Danny Seaborne, Matt Taylor, Scott Golbourne, Alex Russell, Bertie Cozik (Richard Duffy, 59mins), Ryan Harley, Stuart Fleetwood (Adam Stansfield, 68mins), Marcus Stewart, Barry Corr (Richard Logan, 68mins). Subs not used: Oscar Jansson, James Dunne, Liam Sercombe, Troy Archibald-Henville.
Bookings: Tully (13mins), Fleetwood (44mins), Corr (67mins)
Sending off: Tully (52mins)
Scorer: Stansfield (88mins)
Millwall: David Forde, Jack Smith (Alan Dunne, 46mins), Andy Frampton, Paul Robinson, Darren Ward, Danny Schofield, Jimmy Abdou, Marc Laird, Steve Morison, David Martin (Jason Price, 72mins), Chris Hackett. Subs not used: John Sullivan, Adam Bolder, Ali Fuseini, Lewis Grabban, Ashley Grimes.
Bookings: Smith (29mins), Martin (44mins), Frampton (67mins), Morison (85mins)
Scorer: Martin (21mins, pen)
Ref: S. Hooper