League Two Darlo will fancy their chances down at Northampton after they were on top for much of this game.
Darlington took the lead after only eight minutes. Defender Neil Austin found Julian Joachim on the right and the former Aston Villa man put the ball into the path of Gregg Blundell, who made no mistake from ten yards out.
Seconds later Town Captain Chris Doig limped off and he will be a doubt for the replay. His replacement Bradley Johnson had enough opportunities to win the game for the visitors.
In the 21st minute the home side went close to increasing their lead when midfielder Michael Cummins drove the ball against the post, but five minutes later in the 26th minute, the visitors found themselves level.
A quickly taken free-kick found Colin Larkin and his speculative shot from 25 yards caught Darlington keeper David Stockdale out of position.
In the second half Johnson had two early opportunities to put Northampton into the lead. In the 50th minute he headed over from ten yards and then seven minutes later a half volley from even closer flashed past the post.
On the hour mark Cummins headed Joachim's cross over the bar from close range. In the 75th minute John Brackstone was the provider with a left-wing cross that found Cummins inside the area, but again his effort was off target.
As the game drew to a close the visitors almost scored in the 83rd minute through Liam Dolman and then, with only seconds left on the clock, Darlington substitute Pawel Abbott fired over the crossbar from midway inside the area.