Lucas Digne scored a 96th minute equaliser to ensure the points were shared at Goodison Park with Everton eventually drawing 2-2 with Watford.
Everton were 1-0 up via Richarlison's first-half opener against his former team - but a Seamus Coleman own goal on 53 minutes was added to by Abdoulaye Doucoure on 55 minutes to hand Watford a lead away from home.
Gylfi Sigurdsson missed a penalty just three minutes after Doucoure's goal and Everton looked as if they'd be made to rue the miss.
However, Digne's free-kick from 20 yards out right at the death ensured the points were shared at Goodison.
It was only Everton's second home league loss of the season, as they squandered a one-goal lead.
How It Happened...
Everton came into this game in high-spirits despite their disappointing 1-1 draw with Newcastle United at home.
But the Toffees were undefeated in the Premier League at Goodison Park since September, when they lost to West Ham United.
Marco Silva was up against his former side in Watford; and his side made the perfect start at Goodison.
Richarlison, who was also facing his former team; opened the scoring - but there was more than a hint of offside.
Andre Gomes collected the ball and played it to Theo Walcott, who was clearly standing in an offside position, who squared it to the Brazilian and he smashed home with ease.
The Brazil forward grabbed his eighth goal of the Premier League season; with his record-high in a league season being nine goals for America Mineiro in the Brazilian second tier.
Watford had a golden opportunity to equalise just before half-time; when Ken Sema delivered a pin-point cross to Roberto Pereyra, who couldn't direct his header towards goal.
After the break, Pereyra came close once yet again. The midfielder's 20-yard free-kick went just wide of Jordan Pickford's post.
Pereyra was proving a menace and Everton were struggling to handle the Argentine. His shot rebounded off the post and then hit Coleman, and it was all square at Goodison.
It was a brilliant few minutes for Javi Gracia's men and Silva quickly saw his side fall behind to the Hornets!
Pereyra, who was having an outstanding second-half for the visitors stood up an inviting cross to Doucoure at the far post and he headed it past Pickford.
It was some turnaround for Watford; who had score two in as many minutes in front of a stunned Goodison crowd.
The game had really come to life in the second-half and it looked all set to be three goals in five minutes...
Christian Kabasele brought down Yerry Mina and it was a penalty, but Sigurdsson's spot kick was saved by Ben Foster's legs.
Sigurdsson then almost turned provider when his mis-hit shot found Richarlison, who slipped six-yards out and couldn't get up quickly enough to shoot.
There was a roar of "come on!" from the Everton faithful as the fourth official held above his head six minutes of added time.
And in the 96th minute, Digne curled his free-kick over the wall and beyond Foster to score his first goal for Everton.
Relief around Goodison; but a jubilant moment for Digne with his first taste of a Premier League goal - and what a goal it was!
Post-Match Reaction...
Everton boss Marco Silva described the period in which his side went behind in the game as "not too special".
"We lost our focus completely (for Watford's goals)," Silva said. "Those two moments were not too special."
Sigurdsson's second-half penalty miss has raised the question over Everton's penalty taker in the future, but Silva has given him his support.
"Let's see what we can do and analyse the match," Silva added. "Gylfi is scoring many goals for us. He has all of our support."
Silva also believes that Digne's last-gasp leveller showed great "character" to step up and take the responsibility of the free-kick.
"You have good kickers," Silva said. "They work really strong. It showed great personality and character to take that free-kick when people might have expected Gylfi. It's a very good goal."
Watford manager Javi Gracia has insisted if VAR was active in their 2-2 draw; the result would have been different.
"It's difficult to accept because in the second half, we dominated," Gracia claimed. "To concede in the last minute is tough to accept but we'll continue in the same way with the same attitude.
"Only some difficult decisions to accept changed the game in the first-half. After that the team was confident playing the same way."
Gracia was speaking about Yerry Mina not being red carded for a contentious challenge he made in the first-half and Everton's opener being offside.
"I prefer not to say anything about the referees," Gracia added. "If VAR was ready today the result would have been different. I'm very proud of my players."