Things were looking pretty rosy for Tottenham when they took the lead at Vicarage Road, with Lucas Moura forcing an own goal from Abdoulaye Doucoure early in the second half.
As they passed the hour mark, Spurs were on course for an 100 percent record after four matches, which would have equalled their best-ever start to a Premier League campaign and put them alongside Liverpool and Chelsea at the top of the table.
However, they threw it all away. As Watford upped the ante, Spurs seemed powerless to resist and two basic defensive lapses from set-pieces allowed the hosts to fight back and secure all three points, with Troy Deeney and Craig Cathcart heading in the goals.
Lucas Moura looked lively again and was the instigator when Spurs got the breakthrough, but there was little else for Mauricio Pochettino, his players or the fans to smile about.
Tottenham only mustered two shots on target and needed a fortunate own goal to get their noses in front. At the other end, they continue to give away chances too easily while in the middle, Mousa Dembele looked a shadow of his former self.
Spurs' mentality has to be questioned after such a turnaround and when they fell behind, their lack of offensive options on the bench became a problem. Fernando Llorente was the only attacking player in reserve.
Manager rating out of 10
4 -- Few were complaining about Pochettino's team selection and his switch to 3-1-4-2 when Spurs took the lead, but he failed to react when Watford began to fight back. There were warning signs even before the Hornets scored in the 69th and 76th minutes. In the end, the first substitution came 15 minutes after his side had fallen behind. Eric Dier and Victor Wanyama could have added some bite in front of the rearguard but both remained on the bench.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
GK Michel Vorm, 6 -- Watford only had three shots on target and two of them went in. In fairness, Vorm had little chance with either of them.
DF Toby Alderweireld, 5 -- Played some fine long-range passes in the first half and created a chance for Dele Alli with a pinpoint ball over the top, but he struggled defensively in the second half and headed against his own crossbar before the Hornets scored their goals.
DF Davinson Sanchez, 5 -- Had a good first half and kept Andre Gray quiet with his pace, but he too went missing when Watford turned up the heat.
DF Jan Vertonghen, 5 -- Helped to give Spurs some width in the first half and found Sanchez with an arcing cross that was headed over, but he was partly at fault when Deeney headed in.
DF Kieran Trippier, 5 -- The right-back went into the match with a goal and five assists in six Premier League matches against Watford, but he was unable to keep that run going and had a quiet game.
DF Ben Davies, 5 -- Offered little down the left and too often took the wrong decision in possession.
MF Mousa Dembele, 4 -- Deployed in front of the defence, the 31-year-old had a bad afternoon. Watford took control of the midfield after going behind, and it was Dembele who committed the foul on Will Hughes that led to the home side's equaliser. He then lost out to Cathcart for the winner.
MF Dele Alli, 5 -- Sent an early header looping over the bar from Alderweireld's long ball and struggled to make an impact after that.
MF Christian Eriksen, 5 -- Tried to get on the ball and make things happen but lacked his usual influence and, as usual, Spurs suffered as a result.
FW Harry Kane, 5 -- Largely on the periphery and when big moments came, he was unable to capitalise. Had he beaten the defender with a low pass towards an unmarked Lucas, Spurs may well have gone 2-0 up. Kane then sent a late header over the bar.
FW Lucas Moura, 7 -- Spurs' most dangerous player, the Brazilian worried Watford's defenders with his skill and speed while winning the ball back in the hosts' half a few times. It was he who fired in the cross that forced the own goal from Doucoure.
FW Fernando Llorente, NR -- Entered the fray for the closing stages, coming on in place of Alderweireld, but could not provide a leveller.
MF Harry Winks, NR -- Finally replaced Dembele in the 86th minute but it was far too late for him to assume control of the midfield.
DF Danny Rose, NR -- Provided some fresh legs at the death but, again, there was no time left for him to make an impact.