Unique rivalry back with an almighty bang
Sudden death drama - and sheer joy for Rangers. For once, 'Raintown' was sun-dappled. And, as manager Mark Warburton admitted, the blue half of Glasgow has emerged from "a dark place".
The corrosive, long overdue Sunday service was back, with ancient foes wrestling for a Scottish Cup final place. As adverts for this institutional confrontation go, it was compulsive. Edgy, ebbing and flowing.
Perhaps most significantly, there are major ramifications for both clubs - and will be for quite some time. What a sight and encouraging future unfolding now for Warburton. Rangers were simply magnificent at times, the epitome of controlled aggression.
Celtic boss Ronny Deila, meanwhile, trudged up the tunnel with his hand in his pocket - but is the other about to fling open the Parkhead exit door? What a hugely chastening experience for the Norwegian, even though the Hoops are on course to win a fifth successive SPFL title.
Saturday's semi-final victors, Hibernian, skipped off the Hampden turf to 'Sunshine on Leith'. The battle hymns from both Rangers and Celtic fans were also impossible to ignore on an exciting day when the Scottish game received massive enhancement.
Stern images of respective captains Lee Wallace and Scott Brown bore down from billboards, and the more optimistic of the Light Blue persuasion kept bookmakers adjacent to the national stadium busy. Amid this, the sight of an elderly Celtic supporter being guided to the safety of his own end by a Rangers fan was heartening.
The relative lack of Old Firm action in recent seasons due to Rangers' demotion ensured craziness long before kick-off, and an instinctive sense of something special. Assembled media from Germany to Argentina were captivated by the sights and sounds, the blue and green smoke clouding the stands.
Initial skirmishes were dynamic. Celtic's Leigh Griffiths buzzed around, but euphoric waves greeted Kenny Miller's 15th minute goal for Rangers.
Patrick Roberts, Celtic's expensive loanee from Manchester City, drew disbelieving gasps when he spurned an open goal, after Griffiths' shot had cannoned off a post.
Nevertheless, double-chasing Celtic's second-half response was vibrant. Substitute Erik Sviatchenko answered the call, powering home a headed leveller. Both sets of players inched for space, the managers prowled the touchline. Absorbing, razor-wire theatre.
The Light Blues kept their composure in the immediate frenzy. Relative calm - if that is possible here - ensued as extra-time began. Man of the match Barrie McKay's hit was superb - yet substitute Celt, Tom Rogic, swept home. Griffiths whacked the crossbar in the dying moments. Incredible.
Someone had to suffer. Australian Rogic failed to hold his nerve from the spot, sparking incredible scenes from a long-embattled, now ecstatic, Rangers support. How they will dine out on this outcome and a final against Hibernian.
As Celtic trawl through the recriminations, Deila's future cannot be shirked anymore.
On the other hand, for Rangers, the days are appearing so much lighter, following the desperate, bleak years.