Celtic suffered Champions League humiliation as they were taken apart 7-1 by a rampant Borussia Dortmund side in Germany.
Brendan Rodgers' men were their own worst enemies with a defensively diabolical display marked by a bizarrely wide-open approach against a team that made it to the final of the competition just last season.
While this was always the toughest match to circumnavigate in their eight-game cycle, few would have predicted such a comprehensive dismantling.
It all started after just seven minutes when an unlucky break of the ball off Callum McGregor sent Jamie Gittens through on goal. The midfielder was brought down by Kaspar Schmeichel for a stonewall penalty and Emre Can made no mistake from the spot, firing into the roof of the net.
Celtic seemed unfazed and equalised two minutes later when Daizen Maeda ghosted into the box unmarked to turn in Nicholas Kuhn's delicious cross. It was to be a fleeting reprieve.
The game suddenly took on a kamikaze sensibility when Dortmund went back into the lead on the 11th minute when Karim Adeyemi's shot took a wicked deflection off the toe of Auston Trusty and past the flatfooted Schmeichel.
Dortmund continued to threaten and got their reward when Adeyemi got his second with a shot from an acute angle. The strike was clean and powerful but major questions will be asked of Schmeichel, beaten too easily at his near post.
Adeyemi continued his one man war on Celtic's defence by winning a penalty when he was caught by Arne Engles and Serhou Guirassy drilled home from 12 yards.
And Adeyemi wasn't stopping there, blasting his hat-trick just before half-time with an unstoppable low shot after Maeda gave the ball away in a dangerous area.
The one-way traffic continued in the second half with Dortmund grabbing their sixth through the impressive target man Guirassy and a seventh through Felix Nmecha.
As the final whistle blew, it was a humbling night for Rodgers and Celtic but also, given the Parkhead side's absolute domestic dominance, Scottish football.
Here are three key talking points from a night of Champions League pain.
Midfield exposed
While Callum McGregor has enough quality to breeze through the SPFL without having to think about much else than attacking as a deep-lying playmaker, his lack of natural defensive nous was clear here. Celtic have long lacked a defensive midfielder in the mould of former enforcer Victor Wanyama and it's not something Rodgers has moved to rectify in the transfer market. It's a squad gap that becomes very pronounced against elite teams.
That's not to say McGregor received much help from disappointing youngsters Engels or Paulo Bernardo who were also dominated in their duels. The trio looked utterly lost and Dortmund easily found space between them and the defence to create chance after chance.
Unforgiving Euro debut for Trusty
It's early in his Celtic career and this will have been a steep learning curve for the American signed in the summer from Sheffield United. He struggled throughout a baptism of fire in European football and while he wasn't helped by teammates, he was run ragged by the fluidity and power of the Germans' frontline. While the defender won't likely have too many struggles in the domestic game, whether he's up to the huge step-up to this level of football is still an open question after such a fraught display.
Rodgers gets it wrong
While the flow was stemmed somewhat in the second half, it's still a bruising defeat that wipes out the excellent goal difference they created in the first game. There will be justifiable questions over whether the approach was naive considering the quality of their opponents.
Maeda continues Celtic journey
The Japanese winger took his goal well and was the one bright spark in Celtic's side. His prodigious work rate was on display and Yan Couto didn't look too comfortable when squared up one on one. Two goals in as many Champions League games is a fantastic individual return and you wonder if someone in a bigger league might be looking at the package he brings to the table.
