An injury-time equaliser denied the Town an FA Trophy victory at Dorchester.
Leading 2-1 thanks to substitute Stuart Fleetwood's goal, Charlie Clough headed home in a crowded penalty area to set-up a replay at Kenilworth Road next Tuesday.
The Hatters led at the break thanks to an own goal scored in the first 50 seconds by the Magpies' Neil Martin.
Dorchester levelled shortly before the hour through Mark Jermyn's low shot, but it looked as though Fleetwood's goal would seal a place in the second round until Clough's late header.
It all began with Paul Buckle making just one change to the side that drew 2-2 at Mansfield nine days ago with JJ O'Donnell replacing Arnaud Mendy in a strong line-up named for the Hatters' first in a double header against the Magpies.
And that hung-ho selection policy paid dividends just 50 seconds into the action. A Jake Howells shot was deflected into the path of Andre Gray but, with the goal at his mercy, he failed to prod home but to his relief the ball was turned home by Magpies defender Martin.
It could and should have been 2-0 a minute later when Gray sped clear of the home defence but failed to hit the target, but the Hatters were well on top on a sticky pitch and Gray almost forged a chance for O'Donnell on 12 minutes after Howells did well to get to the byeline and cut the ball back from the left.
Dorchester, who came into the game with a proud home record of 10 wins from 11 senior fixtures, almost levelled things up on 15 minutes but a smart save from Mark Tyler – his first action of the game – denied the hosts making it one apiece.
Ten minutes later the Hatters almost went 2-0 up after an end-to-end passage of play when, after a superb sliding challenge from Janos Kovacs denied Ben Watson. Gray then broke at pace downfield but couldn't force home having been outnumbered by home defenders.
It was fast becoming the Andre Gray show as the Town striker continued to run Dorchester ragged and he was inches away with a header from an Alex Lawless cross on the half-hour.
Back came Dorchester though, Tyler getting down smartly to keep pout Sam Malson's scuttling effort as the ball crept towards the bottom corner.
Dan Gosling, the hosts' hero in the FA Cup giant-killing over Plymouth, tested Tyler once more two minutes later when using nifty footwork to cut inside an bend an effort goalwards the Hatters' keeper was equal to.
Gray then somehow spurned a gilt-edged chance to double the Hatters' lead on 34 minutes when O'Donnell and Howells broke down the left with the latter putting a cross on a plate for the striker only for him to miss from inside the six-yard box.
As half-time approached the Town continued to press. Scott Rendell flashed in a cross on 40 minutes with O'Donnell sniffing for the scraps before Gray was thwarted by Jason Matthews in the Magpies' goal moments later.
The second half began at a very sedate pace with a deflected effort from Rendell held by Matthews the only action of the first 10 minutes.
However, after Gray used his pace brilliantly to burst into the box, Dorchester went up the other end and equalised. The Hatters failed to clear their lines following a right-wing cross from Watson, and Jermyn was on hand to sweep a low shot beyond Tyler on 58 minutes.
Buoyed by that it was suddenly all the hosts, and the Hatters had to thank Tyler for a magnificent block to stop Richard Logan's low shot from making it 2-1.
Buckle introduced Fleetwood midway through the second period for Gray, and Logan missed another good chance to put the hosts in front with 15 minutes left when blasting high over Tyler's goal.
The Town almost got their noses back in front two minute later when Matthews flapped at a Howells corner but nobody in an orange shirt could force the ball over the line.
However, the Hatters didn't have to wait long to get the ball in the net when a minute later O'Donnell's cross from the left found Fleetwood unmarked and he finished with aplomb from six yards.
Dorchester almost equalised immediately – only for Tyler to keep the Magpies at bay with a stupendous one-handed save from Clough's goal-bound header.
It was almost 3-1 with five minutes left when Rendell saw a shot saved from six yards following Fleetwood's cut-back and Lawless was unable to turn home at the back post.
But just when it looked as though the Town had done enough a corner from the left was swung in and Clough nodded past an exposed Tyler to ensure the two sides meet again at Kenilworth Road next Tuesday.