Two second-half goals gave Millwall the right to dream that they just might avoid relegation from the Championship and inflicted a major setback on Watford's hopes of gaining the remaining automatic promotion place.
Millwall, who had won only one in 11 before yesterday, are still third from bottom and five points behind Sheffield Wednesday, and safety, with six games to go. Watford, who had been beaten by only Leeds in their previous 12, also have half a dozen to play and now trail the other Sheffield club, United, and promotion, by six points.
Carl Asaba's 66th-minute strike and substitute Ben May's injury-time effort brought this shock result, but none of it would have been possible without the Millwall goalkeeper Andy Marshall, who had the added anxiety of wondering whether his wife was about to go into labour.
Watford were strolling and seemed set to go in front when the referee, Andy D'Urso, awarded a 25th-minute penalty against Zak Whitbread for a dubious handball. Up stepped the Watford captain, Gavin Mahon, who was suffering from a stomach problem, but Marshall saved well to his right and gave Millwall hope where there had been none.
"Marshall was fantastic for us and that save turned the game for us," said Millwall's manager, David Tuttle. "Watford will rightly feel they could have won with a bit more luck, but this time it went with us. It's a great result. We all love Millwall as the fans do and believe we can stay up."
Watford have now missed three of their four penalties this season and the mistakes could cost them dearly. Their manager, Adrian Boothroyd, two years older than Tuttle at 35, had some words of experience afterwards.
He said: "I admire anyone with the guts to take a penalty and we lost because we were attacking so well that we forgot how to defend for a spell and got caught. Despite the result I was happy with how we played. I thought the first half was as good as we've been all season. We'll still go for second place until it is mathematically impossible. I am not interested in the play-offs."
Boothroyd will probably take an interest in the play-offs soon because his side do not look good enough to go up on this showing. Similarly, Millwall have probably left it too late to stay up. And they did not win this easily. Asaba had been a passenger until he scored. Colin Cameron was clear on goal and as goalkeeper Ben Foster advanced he slipped the ball to Asaba on his right to complete the easiest of tap-ins. Millwall broke again, as Watford pressed for an equaliser, to score their second four minutes into time added on when a pass from the captain, Dave Livermore, left substitute Ben May with only Foster to beat.