Josh Coburn completed Millwall's comeback as Alex Neil's side came from behind to beat Watford 2-1 at Vicarage Road.
The Lions trailed at half-time after Mattie Pollock had given the home side a 30th-minute lead with his first league goal of the season.
But the visitors - whose learned on Friday that keeper Liam Roberts must serve an extended six-game ban for his much talked-about foul on Jean-Philippe Mateta - responded well after the break, drawing level through Casper de Norre's 59th-minute effort before Coburn headed the 81st-minute winner.
The victory moved Millwall to within a point of the Hornets who came into the game with hopes of closing the gap to the play-off places.
Watford had started positively, creating an early opening for Giorgi Chakvetadze, the Georgia international cut inside before testing keeper Lukas Jensen with a low shot.
And after surviving a scare when Coburn's close-range shot was blocked, Tom Cleverley's side began to take control, carving out a couple of good chances before Pollock headed them in front in the 30th minute.
Another Chakvetadze run caused problems and led to a shooting opportunity for Imran Louza who placed his shot wide before Mamadou Doumbia failed to make more of an opportunity.
There was a sense a goal was coming though and it arrived after Moussa Sissoko's acrobatic volley was deflected wide.
The visitors did not help themselves as they attempted to deal with the resulting corner, failing to track Pollock's arcing run towards far post where the defender was able to head home unchallenged.
The goal confirmed Watford's dominance but despite controlling the rest of the first half, Cleverley's side were unable to add a second before the break.
And the narrow lead began to look precarious as Millwall made a more positive start to the second half.
The Lions came close to levelling eight minutes after the restart when Joe Bryan almost caught out Watford keeper Egil Selvik with a left-footed free-kick that curled around the defensive wall and into the side-netting.
Watford failed to heed the warning and found themselves back on level terms in the 59th minute after Aidomo Emakhu set up De Norre for the equaliser.
Emakhu did well to move past a challenge by home right back Jeremy Ngakia before pulling a low cross back from the byline that De Norre side-footed home.
Watford's response was limited and they were left empty-handed when Coburn met Tristan Crama's right- wing cross with a glancing header that flew beyond Selvik.
The managers
Watford's Tom Cleverley:
"I think the way we approached it is is a big learning curve for us.
"I've got a lot of young players in there, and we put massive emphasis on the first 10 minutes of the game.
"Well, we have to put the same amount of emphasis on the first 10 minutes of the second half, because we couldn't get out of the rut that we started in, and that's a big learning curve for us.
"I think we made a mistake, couple of mistakes early in the half and we lost a bit of confidence with that.
"We're a team with not much depth on the bench to come off, so we have to stick to our principles. And today it was just too many had an off day in that second half, and they they smelt that and capitalised on it."
Millwall's Alex Neil:
"I think now we can draw a line under the Liam stuff.
"You know, we've supported Liam. Liam's made a bad decision. He's mistimed the challenge. I think it's then been trial by media at that point afterwards, which we are not in control of.
"But internally, it's not really been turbulent for us. You know, we've spoke to Liam. Liam's fine. He understands. He spoke to me, all that sort of it's done. Draw a line under it.
"Liam will serve a suspension. That's the way it is, and then we just move on to the next game."
