Jose Holebas' piledriver condemned Middlesbrough to a fourth defeat in five Premier League outings as Watford snatched a 1-0 victory they scarcely deserved.
The Greece international's 54th-minute strike was of stunning quality, but it came in stark contrast to much of what either side produced during a largely dour 90 minutes.
Middlesbrough created the better of what few opportunities there were and saw four penalty appeals rejected by referee Roger East, some of them with greater merit than others.
But ultimately they were made to pay for failing to produce enough in the final third as the Hornets held sway - they have now taken 10 points from their last five games -- in front of a crowd of 28,131 at the Riverside Stadium.
By contrast, the home side ran out having collected just one point from the previous 12 on offer and knowing that had to change rapidly if they were not to surrender their positive start to the campaign.
The first half unfolded as something of a slog with Aitor Karanka's men dominating possession, but doing little with it.
Stewart Downing scooped a third-minute half-volley over the bar and Gaston Ramirez dragged a left-footed effort wide after exchanging passes with striker Alvaro Negredo three minutes later with the Hornets on the back foot during the early skirmishes.
The Teessiders also had two penalty appeals waved away inside a minute after Negredo went down under the combined attentions of Younes Kaboul and Nordin Amrabat -- the former appeared to have at least one handful of shirt. Downing headed against Amrabat's arm, although from point-blank range, and then whistled a right-foot shot wide from the rebound with Mr East unmoved.
Central defender Ben Gibson came as close as anyone to opening the scoring in the first half with a speculative 35-yard drive on the half-hour, although Negredo might have unwittingly done so two minutes earlier at the wrong end.
Back inside his own penalty area to defend a Watford free-kick, he got to Holebas' cross first and powered a header just over the angle of bar and post in his efforts to clear the danger.
Boro resumed in determined fashion and were appealing for a penalty once again three minutes into the second half when Negredo went to ground under Holebas' challenge, but this time the complaints were muted as the referee waved play on.
Midfielder Adam Forshaw side-footed tamely at keeper Heurelho Gomes after running on to Cristhian Stuani's 52nd pull-back, and Uruguay international Stuani fired just wide from a narrow angle seconds later.
But it was the visitors who took the lead in spectacular style when Holebas latched on to Marten de Roon's clearance and smashed an unstoppable shot high into the top corner, beyond the stunned Victor Valdes.
Ramirez saw further penalty claims waved away after hitting the turf as he was confronted by Miguel Britos eight minutes later. Valdes, who is yet to convince the Boro faithful of his enduring quality, had to field a well-struck Isaac Success shot as time ran down.