A thriller in Pairc Esler saw Down make it past near-neighbours Louth by the skin of their teeth.
After a superb first half performance - albeit with a strong wind at their back - Conor Laverty's men led by nine points at the break. However a brilliant comeback in the final quarter had Louth within a point with minutes left on the clock.
The home side tried desperately to keep possession in the dying seconds before the hooter went but they lost the ball after it sounded and Louth had a two-point score in their sights.
A brilliant dive by Adam Crimmins stopped Tommy Durnin from getting his shot away and Finn Murdock booted the ball over the line, securing the 0-25 to 0-24 victory.
Down began the first half as they intended to continue, with Odhran Murdock winning the throw-in and launching a two-pointer over the bar.
Ryan Magill added a single score from play in the second minute and John McGeough tipped over to give the home side a four-point lead with three minutes on the clock.
Down gifted Louth their fist score in the eighth minute when a breech of the three players back rule resulted in Sam Mulroy pointing from a free but they wouldn't score their next for 21 minutes while the Mournemen continued to impress from back to front with 0-11 on the board by then.
Ceilum Doherty curled over a beauty from play and orange flags were raised courtesy of Danny Magill and Odhran Murdock with a free from beyond the '45. James Guinness put Down into double digits 0-10 to 0-01 with 15 minutes played.
There was a short delay when referee David Gough pulled up injured and was replaced by Cavan's Noel Mooney.
Pat Havern pointed after the restart but Louth got back in the game for a spell with points from Conor McKeever, Mulroy, Ryan Burns and Conor Grimes, narrowing the margin to six 0-11 to 0-05.
Down responded superbly with a one point score and a two-pointer from Havern, followed by a brace from Danny Magill but Burns scored the last two points of the half for the visitors to make it 0-16 to 0-07 at the break.
Odhran Murdock converted a free after the restart but a roar went up from the Louth supporters in the 10,240 strong crowd when Mulroy nailed a two-pointer and one from play to narrow the gap to seven 0-17 to 0-10.
The match and the crowd really heated up after that, with traded scores preceding a fluffed goal chance by Down's Ryan McEvoy and a brace of scores from Danny Magill either side of a second two-pointer by Mulroy.
Crimmins and Down sub Caolan Mooney made it 0-22 to 0-13. But Louth came close to a goal when Donal Kenny's shot pounded off the inside of the post and with that they stormed back.
Three orange flags raised by Mulroy, Craig Lennon and Durnin narrowed the deficit to three 0-22 to 0-19 and while the next four scores were shared, one was a two-point free from Mulroy to make it 0-24 to 0-22
Downey scored two either side of a Havern point and with two minutes left to play Down were just one score ahead, 0-25 to 0-24.
The home supporters were willing Down to hold onto the ball but it was lost at the back through a reckless long pass that went over the line for a kick-out. The hooter blew and Louth had possession.
That was when Crimmins raced forward and threw his body on the line, denying Durnin the last shot of the game and Murdock ended proceedings by kicking out of play.
Down: R Burns; P McCarthy, P Fegan, C Doherty (0-01); R Magill (0-01), P Laverty, M Rooney (0-01); A Crimmins (0-02), R McEvoy; D Magill (0-06, 1tp), O Murdock (0-05, 1tp, 1tpf, 1f), F McElroy, J Guinness, P Havern (0-06, 1tp), J McGeough (0-01)
Subs: C Mooney (0-01) for J Guinness (46), S Millar (0-01) for McEvoy (47), E Branagan for McElroy (50), F Murdock for R Magill (62)
Louth: N McDonnell; D Nally, D Campbell, D McKenny; C McKeever (0-01), P Lynch, C Lennon (0-03, 1tp); T Durnin (0-02, 1tp), C Byrne; B Duffy, C Downey (0-02), C Grimes (0-01); C Keenan, S Mulroy (0-12, 2f, 3tp, 1tpf), R Burns (0-03)
Subs: D McDonnell for Duffy (H-T), A Williams for Lynch (40), P Matthews for Grimes (56), K McArdle for Byrne (56), D McKeown for Keenan (68)
Referee: David Gough (Meath) Sub: N Mooney Cavan (20)
