The live broadcast of this encounter could have gone out under the banner of Who Do You Think You Are? -- but it was Celtic's character, not their ancestry, that was under scrutiny at Fir Park.
The most important questions were posed at the start of each half, first when a horrible blunder by Charlie Mulgrew left his goalkeeper stranded and allowed John Sutton to sidestep Fraser Forster and turn the ball across the unguarded line.
Four minutes after the interval Sutton again planted the ball into the Celtic net, this time from a penalty kick awarded when Emilio Izaguirre was judged to have tumbled Keith Lasley inside the box, although there was a suspicion that the Motherwell midfielder had also kicked the ground. This immediately followed a Shaun Hutchinson header that cracked off the crossbar from a corner kick won when the Celtic defence was again caught leaden-footed.
To add to Celtic's frustrations, when they did force openings they found Darren Randolph equal to the challenge. Three top-drawer saves, from Scott Brown, Anthony Stokes and Kris Commons, kept Neil Lennon's men at bay and if Chris Humphreys had been as astute when he broke free with Sutton and Jamie Murphy unmarked and screaming for the ball inside the box, the damage would have been greater.
Yet if football was a game of simple consequences this would have been a no-contest before kick-off. Celtic travelled to Lanarkshire on a 17-match unbeaten run, and as the majestic masters of the previous Sunday's 3-0 victory over Rangers, who themselves had drubbed Motherwell 6-0 a week earlier. Some, though, learn their lessons while others ignore warnings.
In this case Motherwell had discovered in unforgiving circumstances that laxity against one or other of the Old Firm sides is usually punished mercilessly. Celtic, meanwhile, had been warned that their derby triumph was no more than a shining artefact of the past and that every game is a new chapter.
Another capricious factor was the state of the pitch and the ball's random bounces were undoubtedly a factor in some of the more ungainly lunges that saw passes misplaced and opponents bruised.
The poor surface undoubtedly favoured Motherwell, but the home team were regularly able to compose sweeping moves that caught the league leaders on the turn.
At any event, Lennon was not inclined to use the conditions as an excuse for his team's failings.
"We were poor," the Celtic manager conceded. "We started badly and never got a foothold and you have to credit Motherwell for that. We gifted them two goals and we were poor defensively, poor in midfield and the same going forward.
"Maybe our players had nice things said about them this week and maybe they believed their own hype -- not from the backroom staff, I might add -- but perhaps that's a lesson for them.
"Every game is going to be tough from here on in and they'll have to react to that, but they've generally done that when it's been required this season. We were poor and I've made that clear to the players."
If Celtic were reminded in salutary fashion that consistency is the key to a title challenge, it was also the case that Motherwell have been anxious about their see-sawing form, having recovered from their defeat at Ibrox on February 12 to win against Aberdeen and Hamilton, only to lose in last Wednesday's game at home to St Mirren.
But this was Motherwell's first home win over Celtic since May 22, 2005, an occasion which wrenched the title from Parkhead and despatched it to Ibrox.
Whether or not the latest turn of events has the same effect remains to be seen, but Lennon has not discounted the likelihood of other surprises.
"There will be twists in this story on both sides, I'm sure of that," he concluded. (© Daily Telegraph, London)