Northampton severely dented Newcastle's hopes of staying up in the Gallagher Premiership following a 31-17 victory at Kingston Park.
The defeat still leaves the Falcons seven points adrift in bottom spot and a win for Worcester at home to Gloucester on Sunday would make Newcastle's survival an increasingly forlorn prospect.
But Newcastle hit back in a stirring second half with tries from Rodney Ah You and Tane Takulua to make it 24-17, but Northampton weathered the storm and when Alex Mitchell intercepted Toby Flood's attempted pass with two minutes left – he collected the Saints' bonus-point try for a 31-17 success.
Newcastle actually scored first with a fifth-minute Takulua penalty but the Saints were quickly into their stride to lead 17-3 after just 15 minutes with a Collins double.
An electric break by Rory Hutchinson set up the first in the ninth minute and a backhanded offload from powerhouse wing Taqele Naiyaravoro led to the second in 15th minute, with Biggar converting both and adding a 13th-minute penalty as the Falcons looked shell-shocked.
It seemed they had pulled one back when Simon Hammersley crossed but the pass from Niki Goneva close to the left-hand touchline was correctly ruled forward by the television match official.
Newcastle constantly kicked the ball away and their chase was poor and they paid the price when Collins' crossed for his third try just before half time.
The Saints recycled another average box kick for Cobus Reinach to surge down the blindside and Collins strolled in for a hat-trick, with Bigger again converting for a 24-3 half-time lead.
Newcastle finally got their act together early in the second half with a series of forward drives and from a scrum, number eight Nemani Nagusa surged up to the line and Ah You crashed over, Takulua converting in the 48th minute to trim the lead to 24-10.
It was soon 24-17 with Sinoti Sinoti breaking through and George McGuigan took his offload to send in Takulua for a 55th-minute try, which he converted.
The Falcons simply could not break the Saints defence again despite having the edge in the scrummage and in an injury-strewn closing 20 minutes, Northampton were happy enough to defend until Mitchell's killer fourth try in the 78th minute.