Blackburn rode their luck on the way to snatching a narrow win over a dominant Watford side in the Championship.
A moment of magic from Rovers' Ryan Hedges on the counter-attack 18 minutes from time decided a game which saw the Hornets on top for long spells.
Matheus Martins twice hit the woodwork for the hosts and Rovers keeper Aynsley Pears produced a string of saves to ensure Blackburn's first clean sheet in 13 away games and first win at Vicarage Road in 22 years.
All four of Watford's league goals this season came in the opening 43 minutes of their opening-day win over QPR.
Since that emphatic victory on 5 August, the Hornets have drawn with Plymouth and lost to Stoke and Blackburn without finding the net.
In a low-key opening half, Blackburn's Sammie Szmodics fired straight at Daniel Bachmann on 20 minutes while at the other end Martins saw a low shot from close range saved by Pears.
The lively Martins cut in from the left and thumped the crossbar shortly before the half hour and Rovers defender Dominic Hyam threw himself in the way of Tom Dele-Bashiru's shot after some neat approach play from the Hornets.
After the break, Martins whipped another curler narrowly over and had a similar effort deflected past the upright by Hayden Carter.
Substitutes Imran Louza and debutant Mileta Rajovic both went close for the hosts before Andy Moran came off the Rovers bench a day after his arrival on loan from Brighton, but could only curl tamely at Bachmann with his first touch just before the hour.
The deadlock was broken against the run of play in the 72nd minute when Hedges picked up the loose ball after a last-ditch covering tackle from Ryan Porteous denied the onrushing Lewis Travis.
Hedges dinked the ball past Wesley Hoedt's challenge and juggled it twice before lashing a strike inside Bachmann's near post from a tight angle.
The hosts pressed for a leveller but Rajovic's touch was heavy after a cutback from Ryan Andrews and Martins saw a low strike through a crowd of players excellently tipped on to the upright by Pears.
Ken Sema blazed off target in added time and the final whistle meant Watford's four points from four games is their worst start to a season in 12 years.
Blackburn move up to ninth after a first league win since their opening-day victory over West Brom.
Watford manager Valerien Ismael told BBC Three Counties Radio:
"This is the Championship - it shows when you are on top, you have to take advantage. We missed some chances, hit the crossbar, the post, had some situations in the box blocked. We were only missing the first goal, it would have calmed us and given us confidence.
"We dominated the game. Our press was not right in the first half but in the second it was much better which is why we pinned the opponent in their own half. We have to learn to be more patient when we play against an opponent very deep with the bus in front of the goal.
"We realise opponents are changing the way they play against us, so it's a situation we have to deal with. It's a process, it is ongoing."
Rovers boss Jon Dahl Tomasson told BBC Radio Lancashire:
"I am delighted with the result and the performance. We knew coming to Watford with the quality players they have it could be difficult to dominate the game on the ball, as I normally want to do.
"We chose for great organisation with high discipline, you saw all my boys working hard. I think we defended really well and when you can keep a clean sheet, and I think Watford had only three shots on target, then the team have done a lot of good things.
"I think we could have scored a couple more goals but the resilience and the attitude and the discipline was excellent."
Blackburn midfielder Lewis Travis told BBC Radio Lancashire:
"It was very tough but the boys executed the game plan. It was a great finish from Ryan (Hedges) - it was our game plan just to sit behind the ball and catch them on the counter with the pace we have up front.
"It was a massive team effort - all the lads played well and put a shift in and it was a fantastic performance."
Travis added that his side had dedicated the win to Rovers PA announcer Matt Sillitoe who died this week aged 30:
"We want to dedicate that win to Matt Sillitoe and his family. He was a big part of Blackburn Rovers and we're all thinking about him today. That win is for him."