In the third of The Celtic Way's Moments That Mattered series, we focus on an individual who overcame multiple setbacks to become one of the only bright spots of what was ultimately a dark season in club history...

As stories go, the opening chapters of David Turnbull's Celtic one were littered with plot twists.

A remarkable 2018-19 campaign for Motherwell led to SFWA young player of the year honours; Celtic's interest was piqued as a result.

A Well club-record £3.25million deal was agreed and the then 19-year-old was set to follow a path once trodden by the likes of Joe McBride, Brian McClair, Dixie Deans and Phil O'Donnell.

It collapsed. Turnbull would, medics insisted, require preventative surgery on his left knee and a consequent lay-off of at least seven months. Celtic revised the terms but the two clubs could not agree and the teenage sensation remained at Fir Park in a story that seemed destined to end in a 'what if'.

Fast forward a year and Turnbull - having undergone the knee operation, extensive rehabilitation programme and subsequent first-team return at Motherwell - found himself back in the frame for a Celtic move.

This time there were no hitches. £3million fee, four-year-deal, delighted to sign and all the usual stuff. Yet amid the ritz and the rabble a new Celtic transfer announcement always brings, the naturally quiet-spoken Turnbull let his guard down slightly; enough to admit actually signing for the club after the year he'd just had was, to him, 'the light at the end of the tunnel'.

READ MORE: Robson, Hartley and Celtic’s magnificent seven wins to grab three in a row and honour Tommy Burns

But that tunnel darkened again pretty quickly. A 16-minute debut outing as a substitute in the 5-0 win over Ross County in Dingwall on September 12 gave way only to more sub appearances, often closer to 10 minutes than 20.

It did not get much better and, by the end of October, Turnbull had still played almost three times as many minutes for Motherwell in the three weeks of the 2019-20 season for which he was their player as he had clocked for his new employers in two full months.

Scotland under-21s duty provided some footballing respite, playing an hour or more in each of the Dark Blues' wins over Lithuania and San Marino, but familiarising himself with the Parkhead turf in the same manner remained an impenetrable task.

Then, Covid. That interminable disease that ground society to a halt earlier in the year also stopped any hopes Turnbull had of forcing his way into the Celtic starting picture. Zero minutes followed in November 2020 as he adhered to the self-isolation procedures of the time.

December began in much the same vein as the rest yet a 26-minute substitute's outing during the 1-1 draw with St Johnstone - where he did not misplace a pass - did enough to earn him a start in the next game.

That Perth Saints game was notable for more than Turnbull's sub appearance though. It was the first time the Hoops had avoided defeat in five games but also made it six without a victory; an unacceptable level of malaise had been reached.

It prompted protests outside the ground at a time when the UK Government was rolling out Covid-19 vaccines to society's most vulnerable, that point serving simply to reinforce both the desperate times in which they took place and the sheer anguish of some of the fanbase as 10 in a row began to slip away.

The recriminations of that failure, the way in which it unfolded and the animosity it bred are widely known. It is true the seeds of that particularly bitter harvest were already well sown by the time Turnbull started only his second match for Celtic - against Lille in the team's final game of an already-condemned Europa League Group H campaign - but what unfolded over the next three weeks of December sparked what many remember as the only bright spot of a dark, dark season.

It started at an empty Parkhead with an experimental Lennon line-up; Conor Hazard was between the sticks, Ismaila Soro next to Callum McGregor in midfield and Patryk Klimala up front. Turnbull played as an advanced midfielder in support of the Pole.

The Hoops took the lead from what would become a trademark Turnbull inswinging corner but, in a microcosmic mix-up, couldn't hold on to it for very long.

It was captain-for-the-night McGregor's mistake that led to the Lille equaliser but he would also be the man to restore the lead from the spot after Jeremie Frimpong had gone down upon collecting a Turnbull through ball in the box.

Ex-Celt Timothy Weah drew Lille level for a second time before Turnbull once again made sure the night was his, turning home a low Kristoffer Ajer cross from the right without even breaking stride.

Celtic Way:

It was an impressive enough finish in its own right but even more so in context. Second-ever Celtic start; first in Europe; over a year's worth of injury, illness and selection tribulations weighing heavily on his back. 

The goal, and the performance, was not one of a man bereft of confidence - and both Turnbull himself and his manager acknowledged as much on the night.

"David had a hand in all the goals - I thought he was outstanding," Lennon said post-match. "It was a great finish for the third, I really enjoyed that one.

"You know, it's been a slow-burner for him. He's had the virus, he's missed a month and we had to just break him in slowly. I thought on Sunday [in the St Johnstone game] he came on and made a real positive contribution - he did it again tonight so it gives us a lot of encouragement going forward."

Turnbull himself? True to type he kept it low-key. "It's what I do," he said when asked post-match about his composure and the fact he played a vital part in all three Hoops goals.

The performance did more than just encourage him - it emboldened Lennon too. Turnbull had made his bones now as far as he was concerned, yellow jersey management and all that. After two starts in just over three months, he was in for his second in four days as Kilmarnock arrived at Parkhead. 

They won that one 2-0, Turnbull setting up the second for Shane Duffy from another corner kick and contributing eight opposition-half recoveries, an interception and three loose ball duel wins as the side kept its first clean sheet in any competition since November 1, nine matches earlier.

READ MORE: Anthony Stokes, Neil Lennon and the true start of Celtic's historic second nine in a row

A Scottish Cup win followed - against Hearts on penalties in the delayed showpiece from the previous season - before a fourth successive starting spot at home to a Ross County side that had gone to Parkhead and won for the first time in club history less than a month prior.

The Hoops avenged the 2-0 November loss with a win by the same scoreline and again Turnbull made sure it was he who grabbed the headlines, scoring the opener and earning man-of-the-match honours.

A return to Lanarkshire beckoned - but not to Fir Park. Hamilton Accies' New Douglas Park was the venue as Celtic bestowed a Boxing Day bashing on Brian Rice's relegation candidates.

The performance was such that it prompted Lennon to declare it "outstanding... the best we've played for a long time". Turnbull's contribution on this occasion? Not a man of the match award, that went to Odsonne Edouard, but another goal and a personal xG value of 0.83 - almost double his previous best in his Hoops career - was sufficient reward in itself.

There was but one match left in 2020 by this stage and while Celtic's form had picked up they were still 16 points off Rangers with three matches in hand and a derby coming up immediately after New Year.

For Turnbull, though, the difference a year makes could not have been more stark; 12 months prior he was still in injury rehab, Celtic move in virtual ruins. Now, he was on a frankly ridiculous streak of form and had forced his way into the starting XI with such conviction that his name and number were now as much of a given on the teamsheet as the Celtic badge itself.

Celtic Way:

The final match of 2020 was a trip to Tayside to face Dundee United at Tannadice. Turnbull would play behind strikers Leigh Griffiths and Odsonne Edouard and once again outshine them both - with another goal, past future Celtic team-mate Benjamin Siegrist, and another man-of-the-match award making its way into his back pocket.

"He had to wait a wee while to get to the pace of how we want him to play," Lennon said in the aftermath of the 3-0 Tannadice win. "But now he's in excellent form there's no reason for me to leave him out."

He didn't leave him out. Nor did Lennon's interim successor John Kennedy. After toiling for game-time in October and logging none at all for Celtic in November, the 495 excellent minutes he put in throughout the final month of the year was enough to ensure he started every single remaining game in Celtic's season, bagging a further five goals and four assists as well as the club's player and young player of the season awards in the process.

The campaign is remembered vividly, viscerally and with extreme prejudice - except for Turnbull's contribution. He said when he joined that Celtic were the light at the end of his dark tunnel; when the final whistle of the season had blown he had become that very thing to the support.

The statisticians will note that, by the time those Hogmanay Zoom chats were being scheduled and the calendar flipped over into 2021, Turnbull had played seven games in December.

He started six, scored four goals, won four man-of-the-match awards and laid on two assists.

More important was the one Celtic career those things ignited.