Saints endured another tortuous Twickenham experience as they shipped seven tries in a 50-21 evisceration at the hands of Harlequins.
It was the second time the green, black and gold had been humbled at English rugby HQ this season, following the 55-24 Aviva Premiership opening-day defeat to Saracens.
Just as on that occasion, Saints shipped the bonus point before the break and concede a half-century of points.
Rob Horne, Nic Groom and Mike Haywood did manage to score after half-time, but the defeat always looked inevitable once Quins took the lead.
It was another Northampton horror show to end 2017 and they have now suffered 12 defeats from their past 13 matches in all competitions.
That record includes seven successive Premiership losses and new coaching consultant Alan Gaffney, who starts work on Monday, has a huge job to do ahead of next Saturday's home game against Gloucester.
Saints had headed to Twickenham hoping a few days off over Christmas would pay dividends and, after a scruffy opening seven minutes, they seemed to have got into their stride.
A fine counter-attack led by Ahsee Tuala resulted in Luther Burrell being bundled into touch by England full-back Mike Brown.
The ball failed to bounce kindly for Burrell and Quins got a let-off which they soon made the most of as Dave Ward skipped through a gap and sidestepped Harry Mallinder to score.
Marcus Smith slotted the conversion to make it 7-0 after 12 minutes and Saints then just about escaped the concession of a second try.
Mallinder's pass was intercepted by Tim Visser, who eventually dived over the line, but Jamie Gibson had just done enough to ensure the winger's foot was in touch.
Quins did grab a further three points soon after as Smith landed a penalty and the fly-half's moment of magic quickly helped to set up another score.
Smith chipped the ball over Saints' defence and after some tidy handling from the home team, Jamie Roberts offloaded to Charlie Walker for an eye-catching score.
Smith added the extras and it was already turning into another chastening day for Saints, who were wondering where to turn as Quins, who had lost five of their past six matches in all competitions, ran riot.
It was to get even worse on 21 minutes as Visser ran in unopposed out wide and Smith again converted, taking the score to 24-0 and prompting flashbacks of the Sarries defeat.
Saints were then forced into an early change as Tuala hobbled off and George North made his return from a knee injury after more than two months out.
North took a knock during his first involvement but fought on, which was not the case for his team-mates as they shipped the bonus-point try seven minutes before the break.
Danny Care was the man to score as he cruised over close to the posts, almost looking embarrassed to have bagged his team's fourth try so early.
Smith again applied salt to the gaping wounds with the conversion and Saints suffered another injury blow before the break as Piers Francis clashed heads with Roberts.
That brought Stephen Myler into the action as he made his return from a calf injury, but Saints headed in 31-0 down at half-time with few signs of a comeback from the away side.
And the second half was to continue in the same manner as a floated pass was misjudged by Mallinder, and Visser again walked the ball over the try line.
Smith missed the conversion and Saints finally exerted a little pressure, forcing James Chisholm into the sin bin for offside as he knocked the ball on close to his own line.
Saints took immediate advantage as Api Ratuniyarawa dropped the ball and it fell kindly for Horne, who picked up to score.
Myler converted and Saints soon scored again as scrum-half Groom spotted a small gap and scored.
Myler's conversion cut the gap to 22 points with 25 minutes remaining, but Quins soon extinguished any sort of Saints hope.
Ben Foden struggled to deal with the bouncing ball and after Quins worked hard to regain possession, Care dived over for his second try.
Smith converted and Saints were to suffer the ignominy of shipping a half-century again as Mat Luamanu powered over and Smith slotted the conversion again.
There was still 10 minutes to go and time for hooker Haywood to cement his status as Saints' top scorer as he dotted down.
Myler again converted to take Saints up to 21 points, but it was far too little, far too late as Saints were left to reflect on another sizeable defeat.
Harlequins: Brown; Walker, Alofa Alofa (Cheeseman 64), Roberts, Visser (Lang 72); Smith, Care (Kitto 64); Marler (Boyce 60), Ward (c), Sinckler (Swainston 65); Merrick (Matthews 60), Glynn; Chisholm, Robshaw (Wallace 75), Luamanu.
Saints: Mallinder; Tuala (North 25 (Reinach 64)), Horne, Burrell, Foden; Francis (Myler 38), Groom; Ma'afu (Van Wyk 64), Hartley (c) (Haywood 59), Ford-Robinson; Ratuniyarawa (Paterson 64), Lawes; Wood, Gibson, Harrison (Nutley 59).
Referee: JP Doyle