Clyde came from 2-0 down at half-time to take all three points at Berwick with substitute Karin Belmokhtar scoring two, including a dramatic 90th minute winner.
First half goals from Cedwyn Scott and Jack Ogilvie had put Rangers in the driving seat at the break.
Butt two goals in eight minutes at the start of the second half from David Goodwillie and replacement Belmokhtar saw the visitors hit back to equalise before Belmokhtar netted the winner as the game crept into injury time.
There was little between the sides in the opening quarter of an hour, with neither keeper being tested.
Then, on 17 minutes, Goodwillie found a gap on the edge of the box for Clyde and managed to get in a shot which rebounded off the inside of Sean Brennan’s right hand post.
Just two minutes later Daryl Healy pulled a shot across the Clyde goal from an acute angle.
The opening goal came for Rangers in the 27th minute when Healy played Scott through the middle and the striker sidestepped his marker before confidently shooting low into the bottom corner past Blair Currie.
On 37 minutes Brennan made his first real save of the game when he got down to smother a Barry Cuddihy shot.
Berwick then doubled their lead on 40 minutes when Gary Phillips made a strong run through the middle and set up Ogilvie who coolly slotted past Currie to make it 2-0 at half-time.
But Clyde hit back with two goals in the first nine minutes in the second half and suddenly the sides were level again.
Just a minute after the restart the Bully Wee caught Rangers cold when Goodwillie netted from close range after the ball was cut into the box from the left by Martin McNiff.
And after Mark Lamont blazed wide, substitute Belmokhtar levelled it up at 2-2 after Robert Wilson lost possession in the opposition half and Clyde broke quickly.
Minutes later, Goodwillie almost gave Clyde the lead when he broke through the middle but dragged his shot inches wide of the post past an outstretched Brennan.
As Danny Lennon’s side continued to press Brennan went full stretch to deny John Rankin with a shot from outside the box.
In a dramatic finale Belmokhtar forced a last minute winner from close range after Rangers’ keeper Brennan made a fine double save.
Clyde manager Danny Lennon said: “That was a great example of desire and commitment shown by our players. It also showed just how important the squad system is, as all the players who came off the bench made an impact, none more so than Karim, who scored two goals.
“We didn’t play badly in the first half but found ourselves 2-0 down. I told the players at half time the next goal was the most important one, and we got it within 90 seconds, which set us up for a tremendous second half performance.
“That’s four wins out of four, which is great, not just for the players, but for the fans as well - once again they were magnificent today.”