For 75 minutes Chester FC were second best to a strong, well organised Grimsby Town team, who gave a performance befitting of title contenders.
But two goals in the space of nine minutes turned the game on its head and the Mariners were all at sea amid a blue-shirted storm in a pulsating finish.
Ollie Palmer's first-half effort had the visitors ahead at the break and when Jon-Paul Pittman made it 2-0 with just over 20 minutes remaining the game seemed won.
Ben Heneghan struck with 15 minutes left and in an instant Grimsby looked far less assured so it was no huge surprise when the Blues equalised through John Rooney's penalty.
There were chances for both teams in a thrilling end but the game shared, and understandably the home fans celebrated the point more like three.
Following the 1-0 win at Torquay United midweek, Steve Burr suggested there would be changes and the manager was true to his word.
Craig Mahon dropped to the bench and Gareth Roberts and John Rooney were rested with starts for Kane Richards, Matty Hughes and Ibou Touray, who had not featured since being sent-off at Altrincham on New Year's Day.
George Thomson, who had netted the winner in Devon, retained his place with Hughes, Richards and Oliver McBurnie joining him in an attacking line-up.
Grimsby came up short in the play-offs last term but had shaken off that disappointment to mount another strong promotion challenge.
Four straight wins had given the Mariners momentum at the right time of the season and manager Paul Hurst retained the team that won 2-1 at Woking last time out.
There was no place for leading scorer Lennell John-Lewis, whose planned return following the birth of his first child was put on hold by a knock picked up in training.
Grimsby made the more promising start with Shaun Pearson's header hitting team-mate Aristote Nsiala and Craig Disley forcing Jon Worsnop into action with a shot on the turn.
Chester's first real attack on 11 minutes should have resulted in them taking the lead, Nsiala surrendered possession and Thomson's excellent pass put McBurnie in on goal but he couldn't get the ball under control, allowing the Mariners to recover.
Jack Mackreth, who had a short spell with the Blues, was giving Touray a rough ride down the right and Grimsby remained the more dangerous.
Nathan Arnold might have done better in the 17th minute when he steered Ollie Palmer's chipped cross over the crossbar but the opener soon arrived.
A clever exchange of passes opened up the defence and Jon-Paul Pittman released Palmer, who lofted the ball over Worsnop from six yards, to give his team the lead on 22 minutes.
Grimsby deserved to be in front and continued to control proceedings with Palmer causing problems and the Blues finding it tough to break the visitors down.
Chester lost Thomson on 35 minutes to an ankle problem as Mahon came on and the pattern of the game remained the same.
Pittman should have doubled the lead in the 39th minute when he burned Michael Kay for pace however Worsnop stood up well and deflected the forward's shot behind.
Chester could consider themselves fortunate to go into half-time just one goal down and would need a significant improvement in the second period to get something out of the game.
Grimsby had the first sight of goal following the restart with Pittman flashing a shot into the side-netting from close range.
Hughes got the better of Gregor Robertson a couple of times and Brad Abbott couldn't quite find Richards with his cut back as the Blues gave a little more cause for encouragement.
Ben Heneghan denied Nathan Arnold with an important block at the other end but Chester had grabbed the initative and looked capable of getting back on terms.
However, the Mariners came through the storm and after a period of sustained pressure, doubled the lead in the 67th minute.
Worsnop produced a superb save to tip Arnold's shot onto the post and Pittman was quickest to react, slamming the rebound home from close range.
Rooney replaced Richards and Mahon brought a decent stop out of James McKeown with a shot from 20 yards but Chester's chance looked to have passed.
Grimsby replaced the impressive Palmer with defender Danny Parslow and prepared to close the game out, but a goal out of nothing had them rocking with 15 minutes to go.
Ryan Higgins' cross from the right reached Heneghan and the centre back blasted the ball past the dive of McKeown.
Chester sensed the comeback was on and began to pour forward in numbers with Mahon a growing influence on the game and Hughes troubling Gregor Robertson.
Grimsby's grip on the game had gone and the Blues levelled with five minutes remaining when Rooney converted a penalty.
Higgins found Hughes and he nipped in front of Robertson, who clipped his heels giving referee Martin Coy little choice but to point to the spot with and Rooney dispatched the spot kick with confidence.
It was an incredible turnaround but far from the end of the drama as both teams chased a winner.
Worsnop denied substitute Christian Jolley with an outstanding point-blank save, Kay made a last-ditch block from Arnold and Craig Hobson, who had replaced Abbott, might have won it at the death but for McKeown's best save of the afternoon.
Chester FC: Worsnop, Higgins, Kay, Heneghan, Touray, James, Abbott (Hobson 90), Hughes, Thomson (Mahon 35), Richards (Rooney 67), McBurnie.
Subs: Viscosi, Charnock.
Goals: Heneghan 75, Rooney 84 (pen).
Grimsby Town: McKeown, Magnay, Pearson, Nsiala, Robertson, Mackreth, Disley, Clay, Arnold (Jolley 86), Pittman, Palmer (Parslow 72).
Subs: Bignot, Brown, Hannah.
Goals: Palmer 22, Pittman 67.
Referee: Martin Coy (Durham).
Attendance: 2,916.
