Arsenal threw away a two-goal lead as Roberto Pereyra's late penalty salvaged a 2-2 draw for Watford at Vicarage Road.
Pierre-Emerick Aubameyang put the Gunners in front to open the scoring after 21 minutes and finished off a fine team move to grab his second just after the half-hour mark.
But an error from Sokratis Papasthaopoulous allowed Tom Cleverley to get one back for the hosts and Pereyra slotted home from the penalty spot after being tripped by David Luiz to rescue a late point.
Unai Emery welcomed back Mesut Ozil for his first Premier League start of the season with Alexandre Lacazette out injured, while Dani Ceballos also returned.
The Gunners spent the first quarter of an hour under pressure as Watford began brightly with Gerard Deulofeu impressing on the left.
But the north London side made it count on the break when Sead Kolasinac burst forward and laid it off to Aubameyang, who turned and fired a low shot into the corner past Ben Foster.
The visitors doubled their advantage after the half-hour mark when Aubemayang tapped home after a fine team move involving Ozil and Maitland-Niles.
Having looked comfortable for the majority of the first half, Arsenal came under scrutiny in the second and paid the price for a poor defensive mix-up as Sokratis' pass was intercepted by Deulofeu and Cleverley finished from close range.
The hosts sensed Arsenal were there for the taking and soon found their equaliser when Luiz tripped substitute Pereyra inside the area. The playmaker stepped up to take the penalty and sent Leno the wrong way.
Suddenly Watford had their eyes on a famous victory and they should have got it when Ismaila Sarr found Abdoulaye Doucoure unmarked but the Frenchman struck straight at Leno from six yards out in stoppage time.
Arsenal's collapse in the second half will again pose questions about their backline while Watford's search for a win goes on, but with more displays like that, it won't be long until they end their drought.
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