Celtic FC were on the verge of registering their third draw at the Camp Nou in eight years until Jordi Alba stunned them with a 94th-minute winner from close range to confirm FC Barcelona's Group G leadership.
A first-half own goal from Javier Mascherano rewarded Neil Lennon's team for playing with calm intelligence and although Andrés Iniesta equalised on the stroke of half-time and David Villa hit the post in second-half added time, goalkeeper Fraser Forster appeared to have earned Celtic a valuable point. That was until Adriano arced in a perfect right-wing cross and Alba applied the finish.
However, what would have concerned Blaugrana coach Tito Vilanova is that Barcelona helped make their night more difficult by ignoring the cardinal rule of taking chances when they arrive. Long before Celtic took the lead the home side should have done so. Iniesta's visionary pass split the green-and-white defence and although Alexis Sánchez reached the ball before Forster he somehow skewed the ball past both keeper and far post.
For Barça to threaten properly it took the arrival of Marc Bartra, chosen at centre-back for only his third UEFA Champions League match, in the box to connect with an Iniesta centre and force a save from Forster. The value of that stop was doubled when the Scottish champions went in front not long afterwards.
Charlie Mulgrew's free-kick was nodded on by Giorgios Samaras but the ball diverted past Víctor Valdés off Javier Mascherano. Cue wild celebrations up in the highest part of the stadium where around 5,000 visiting fans roared their delight.
Barcelona reacted. Lionel Messi buzzed two free-kicks into the netting above Forster's crossbar, and another Iniesta service gave Bartra a second header which he fluffed. Fortune didn't favour Celtic in that Samaras, author of much of the danger for the hosts, twisted his ankle just before the break and had to be replaced by James Forrest.
And within moments Barça were level. Messi slipped a pass into Iniesta and when the midfielder played a wall pass with Xavi he was able to reach the return and stab home a sweetly constructed goal.
To Celtic's great credit their second-half display did not waver one centimetre from the game plan. Low strikes from Messi and Iniesta as the match wore on did not particularly test Forster's reactions, though before the final whistle he needed to excel to repel the 2011 champions.
His first golden moment came on 68 minutes when Alexis and Pedro Rodríguez combined to feed Messi with an opportunity that he volleyed from close range and the Englishman reacted brilliantly to parry. Five minutes later Messi had a point-blank header from which he looked destined to score but the keeper somehow bettered him.
Sadly for Forster and his team-mates, Alba stole in for the final word just when it seemed their hard work had borne fruit.