Mullin slipped home his tenth League Two goal of the season in the 73rd minute to cancel out two fabulous strikes from Lee Beevers and Scott Kerr.
Stanley midfielder Andy Todd must not be forgotten either, as he grabbed a first half equaliser with a stunning right-foot volley in the 22nd minute.
Despite going behind twice in this pulsating draw, the hosts were actually the better side for much of the 90 minutes.
Without having too many shots on goal, they had more of the possession as they tried to haul themselves clear of the dreaded drop a zone.
And fortunately for boss John Coleman and their supporters, Stanley were able to prevent a fourth defeat in five games.
Beevers opened the scoring, in the 14th minute, when he latched onto a well worked Lee Frecklington corner that was fired low to the edge of the box.
The right0back composed himself before firing home his right-foot volley to give substitute goalkeeper Przemyslaw Kazimierczak absolutely no chance.
The big Polish goalkeeper, on loan from Bolton, was called into action far earlier than he expected when Liverpool goalkeeper David Martin, also on loan, was forced off with an ankle injury just three minutes into his debut.
Then it was definitely a case of 'anything you can do, I can do better' with Todd, who controlled a weak Nat Brown clearance, before smashing home his volley across Alan Marriott into the bottom left corner on 22 minutes.
Then to complete the goal of the game competition that was clearly developing, Imps midfielder Kerr took advantage of Tony Grant's unfortunate deflection to lob Stanley's 18-year-old keeper.
But Stanley kept on pushing, despite time running out and got their reward when Mullin eased the ball under Marriott with 17 minutes remaining.