Rangers' rejuvenation under caretaker boss Graeme Murty came to an abrupt halt with a 3-1 defeat by St Johnstone at Ibrox.
The Govan side went into the game on the back of four successive Premiership wins for the first time in a year and got off to a flier with a goal in the fifth minute from Colombian striker Alfredo Morelos.
However, Saints midfielder Blair Alston thundered in a leveller five minutes later and second-half goals from Denny Johnstone, on loan from Colchester United, and his replacement Graham Cummins within a minute of coming on gave the visitors their first league win at Ibrox since 1971.
While Tommy Wright's men moved into sixtth place, Rangers dropped to third in the table behind Aberdeen and leaders Celtic with the spotlight on the club's search for a permanent boss sure to intensify following such a dismal performance.
There was an early scare for the home side when Johnstone, back in the St Johnstone side along with Chris Millar, Stefan Scougall and Liam Craig, beat Gers keeper Wes Foderingham in an aerial duel only to see his header slip just past the post.
However, it was Rangers who forged ahead when midfielder Ryan Jack, back from suspension, drove forward and slipped the ball to Morelos who drove a right-footed shot from 14 yards across keeper Zander Clark and into the far corner of the net.
It was the 21-year-old striker's 11th goal of the season and third in three matches and should have settled the home side down.
However, in the 10th minute Alston's left-footed drive from 22 yards flashed past the diving Foderingham for the equaliser to open his account for the season.
The goal infused the Govan side with some anxiety and while they bossed possession, their attacks lacked the zip and guile to unsettle the well organised Saints defence.
By half-time there were rumblings of discontent among the Rangers supporters who had noticed the visitors growing in confidence towards the break.
Referee Don Robertson had to work hard at the start of the second half to keep control of what was turning into a scrappy game and the Perth side continued to grow in confidence.
Rangers could not find any rhythm against a dogged Saints who were menacing on the break, confirmed in the 61st minute when Johnstone almost casually headed a Craig cross from the left past Foderingham.
Murty immediately replaced Daniel Candeias with Niko Kranjcar and Rangers stepped up the pace but it was fuelled by desperation and when a James Tavernier cross was headed over by Josh Windass it brought some groans.
In the 70th minute Saints replaced Scougall with David Wotherspoon and Johnstone with Cummins, who immediately drove in the third from inside the box with what was also his first goal of the season to stun the home fans and seal a shock win.