Town suffered a derby defeat to Watford in the lunchtime kick-off at Vicarage Road, with the hosts climbing to within a point and a place of the Hatters in the Championship table.
Watford took all three points from the first derby to be played in front of fans for 16 years with two goals in each half, Keinan Davis and William Troost-Ekong netting before half-time, Joao Pedro and Ismaila Sarr scoring after the break.
The Hatters were reduced to ten men with substitute Gabe Osho shown a straight red card in the 83rd minute for a late challenge on Ken Sema, with the near-2,000 travelling support heading home disappointed, but still giving their team a tremendous ovation at the final whistle.
Following the 1-0 victory away at Norwich in midweek, captain Sonny Bradley returned to the starting line-up with Dan Potts named on the bench, although both were struggling with illness that had ripped through the Hatters squad overnight.
Henri Lansbury had been unable to travel due to the bug, while Luke Berry was also listed on the teamsheet, but unable to take part having become unwell in the build-up.
Alfie Doughty kept his place in the team, but moved to wing-back with Amari'i Bell filling Potts' berth on the left side of the three centre-backs, whilst Luke Freeman came into midfield.
Elijah Adebayo joined Carlton Morris up front, with Harry Cornick starting on the bench along with fellow forward Cameron Jerome.
Town got off to the worst possible start when they fell a goal behind inside the first three minutes, with Davis volleying Hassane Kamara's left-wing cross in from close range.
Allan Campbell came within an inch of of levelling three minutes later, but his shot fizzed just the wrong side of the post after Morris had done well to control Bell's cross from the left.
Freeman headed Tom Lockyer's ninth-minute cross straight at home keeper Daniel Bachmann after good build-up play on the right, before Ethan Horvath pulled off a wonderful left-handed save to keep out Sarr's 20-yarder.
Bradley was the first player into referee Bobby Madley's notepad for a perfectly timed challenge on Joao Pedro, right in front of the linesman, in which the Hatters captain clearly played the ball against the Watford forward before he went over.
Davis, who might have been booked for over-celebrating his goal in front of the Hatters supporters but received a quiet word along with his captain, Craig Catchcart, instead, was soon shown yellow for dissent after a tangle with Bradley.
Then Edo Kayembe tested Horvath from outside the area on the half-hour, before Madley gave another strange foul against Morris for a foul on Gosling, when it appeared that the offence had been committed by the home defender.
Adebayo soared above Bachmann to head a Freeman cross onto the roof of the net on 35 minutes, and Horvath needed to race off his line to save from Davis with his feet after the Watford striker had spun Bradley just inside the area.
It was 2-0 on the stroke of half-time when Troost-Ekong poked home from close range after Davis had headed Pedro's deep cross back from the far post, with the aid of a deflection of Campbell to take it past Bradley and along the face of goal.
Jones made a change at the break, bringing Gabe Osho on for Bradley, and it was the substitute who - along with Lockyer - almost got on the end of a left-wing corner from Bree, but couldn't connect as the ball flew across the six-yard box.
It was 3-0 in the 57th minute when Pedro intercepted Horvath's attampted pass to Lockyer on the edge of the area, and beat the USA international with his right-footed finish.
Jones immediately made a second substitution, bringing on Cornick in place of Freeman, and it was the Hatters who had the next chance, but Morris couldn't get enough purchase on his header to steer the ball past Bachmann, who gathered on his line.
Cornick saw a 71st-minute shot fly past the far post after being teed up by Morris to the left angle of the area, then Clark had Bachmann diving low to his right to keep out a skidding 25-yarder.
The hosts added a fourth ten minutes from time when Sarr cut inside Bree and curled his effort into the bottom corner of Horvath's net, then Osho was dismissed three minutes later with the Town's seven-match unbeaten run over by the time Horvath produced another fine save to deny sub Yaser Asprilla in injury-time.
Thank you to every Hatter who sang their hearts out at the stadium, as well as the thousands watching at home on iFollow. Your team are ninth in the table on 24 points, with Watford a point and place behind in tenth as we head into next Saturday's date with Sunderland at Kenilworth Road.
Goals:
Davis 3, Troost-Ekong 45, Pedro 57, Sarr 80
Att: 19,282 (1,954 Hatters)