All Black Bruce Reihana grabbed a European lifeline for Northampton and scuppered Glasgow's brave quest to salvage some big-stage pride.

The full-back bagged two great tries to make sure of the vital bonus point to give Northampton a back-door ticket into the quarter-finals as one of the top group runners-up.

Glasgow had looked on course for a shock first win of a dismal campaign as they opened up an interval lead.

But their resistance ended when Saints staged a strong fightback in the wake of an ear-bashing from coach Budge Pountney.

Having started in bright and confident style, it was Glasgow who almost broke the deadlock midway through the first half.

Captain Jonny Petrie made the initial break before linking with fellow back row Andy Wilson. The young flanker looked destined to score, only to be hauled to the deck just a couple of paces short of the line.

Warriors kept up the momentum, and stand-off Dan Parks was narrowly wide with a drop-goal attempt.

Parks was quickly back in the spotlight to give his side a deserved lead with a straightforward penalty from 24metres following an offside verdict by Welsh referee Nigel Whitehouse.

Saints were stung into a session of attacking action of their own - and they snatched the initiative almost immediately.

Wing John Rudd surged into the 22 and popped a superb contact pass to Reihana, who powered over for the first try. Paul Grayson's conversion crashed back off the upright.

Glasgow replied in positive fashion as Petrie embarked on another promising run, and then Sean Lamont clattered through five challenges before being halted with support men slow to get close to him.

All was not lost, however, and just two minutes later Parks slotted his second penalty from close range to grab back the lead for the enterprising visitors.

At the other end, Lamont had to show his defensive talents to barge Rudd out of play after more great work by full-back Reihana.

Rudd and Reihana looked set to break through again for Northampton, but it was Glasgow who ended up with a remarkable touchdown.

Lamont's anticipation was spot on as he raced in to grab a floated pass out of the air on his own 22 - and with all the home markers committed, he was left with an unopposed cruise to the target.

Parks slotted the extras to give the Scots an unlikely eight-point cushion, stunning the sell-out crowd of more than 12,000 into silence.

The visitors suffered a setback in the dying seconds of the half, however, when Kenny Logan was sent to the sin-bin for deliberate obstruction.

Furious Pountney made wholesale changes for the restart - including the introduction of Tom Smith - and right away Saints looked much more hungry and potent.

After a bout of heavy pressure, it was no surprise when Ben Cohen battled through for the second home try - converted by substitute Shane Drahm.

Glasgow enjoyed a reprieve when Drahm was off the mark with a penalty. But their resistance buckled again as number eight Mark Soden claimed touchdown number three, and Drahm safely converted.

Parks clawed back three points with an angled penalty, but Reihana's second try and Drahm's kick made sure for Saints.

There was still time for captain Steve Thompson to add another, before Glasgow had the last word with a scrambled score by Graeme Beveridge.