The Hatters suffered a fourth away defeat in a row as high-flying Middlesbrough won 5-1 at the Riverside Stadium.
Manager Rob Edwards made five changes to the side that beat Cardiff 1-0 at Kenilworth Road three days earlier, but his team were broken by four goals in 24 minutes either side of half-time, with Delano Burgzorg and Finn Azaz both netting two, and Emmanuel Latte Lath also on target.
Substitute Jordan Clark netted his third goal of the season with 13 minutes left to reduce the arrears, but it was the hosts who went soaring back into the play-off places.
The Hatters had started well, with a couple of dangerous looking crosses from either flank courtesy of Tahith Chong and Liam Walsh, although it was Boro who had the game’s first attempts on goal, Hayden Hackney and Luke Ayling both firing over the bar.
Cauley Woodrow, making his first start of the season, had the Hatters' first shot on target - a 25-yarder from the right side of the area that Dieng punched clear - before Walsh, who had been excellent in the early stages, dragged an effort wide from just outside the box.
But Boro took the lead on the half-hour, Burgzorg running onto a loose ball just inside the Town area after a well-worked corner routine from the right.
Town could consider themselves unfortunate to be a goal down having started the game well, but the hosts took complete control of the game two minutes before half-time when Latte Lath controlled Azaz's chipped pass on his chest, turned and placed a left-footed finish into the bottom corner past Kaminski.
The Town keeper had to be alert to prevent it being three by half-time as he saved a Ben Doak thunderbolt at his near post, but Town headed in at the break needing to regroup.
Edwards made one change at the interval, with Victor Moses on in place of captain Amari’i Bell, and Daiki Hashioka switching to left wing-back, with the ex-Chelsea man on the right.
But before they knew it, the Town were three and then four down, and well and truly out of the game.
First, Hackney set Doak clear on the right and the Scotland international cut back for Azaz to curl into the top corner five minutes after the restart.
In a rare glimpse of attacking intent, Chong went on a mazy run down the left and set up Woodrow for a shot that was saved by Dieng.
But within seconds, Boro went straight up the other end and made it 4-0 with Burgzorg netting his second of the game after Latte Lath had won the ball ahead of McGuinness, who was the last defender, and played the Dutch forward in for an open goal.
The Town boss made four more changes, immediately introducing Tom Krauß and captain Carlton Morris for Baptiste and Woodrow, before adding Clark and Marvelous Nakamba to the fray just before the hour, in place of Adebayo and Walsh.
The arrears were reduced on 77 minutes when Krauß won the ball in midfield and fed fellow sub Clark to his left, with the former Accrington man checking back onto his right foot to fire past Dieng for his third goal of the season.
But it was never going to be enough to spark a comeback as Azaz curled in from the edge of the box late on, and the Hatters brilliant travelling support of almost 700 fans were left to head home disappointed.
We thank every single one of you for your passion and commitment in making a 200-plus mile journey for a 12.30pm kick-off at the other end of the country.
See you back at home for Hull after the international break.
Full XI: Kaminski, Hashioka, Mengi, McGuinness, Holmes, Bell (C) (Moses 46), Baptiste (Krauß 55), Walsh (Nakamba 59), Chong, Woodrow (Morris 55), Adebayo (Clark 59).
Subs: Krul, Andersen, Mpanzu, Brown.
Boro: Dieng, Ayling (C), A. Morris, Clarke, Burgzorg, Edmundson, Doak, Dijksteel, Azaz, Hackney, Latte Lath.
Referee: Tony Harrington