If Robert Louis Stevenson was alive today, he might be sitting down this evening to begin the sequel to Dr Jekyll and Mr Hyde, a follow-up based on the split personality of the Scotland rugby team and what they delivered in one of the most surreal Test matches the game has ever seen.
The end-game was cruel for Gregor Townsend's players as they tried to hold on to what would have been the comeback victory of the ages, a win that would not only have brought an end to 36 years of disappointment but also taken its place alongside anything else the Calcutta Cup has thrown up in terms of drama and intrigue.
What we saw when George Ford saved England's skin was genuine sporting despair from the Scots. We have seen it before in this place, of course. Four years ago, Scotland looked like they were about to beat Australia in the World Cup quarter-final only to stumble and fall late on.
We saw that kind of angst again on Saturday. Greig Laidlaw's haunted man look. Hamish Watson's stare into middle distance. The slow shake of the head from Stuart McInally. The ironic smile from Finn Russell. These were the men who almost climbed Everest. Almost.
'What kind of madness was this?'
Every Scottish rugby fan will feel like they spent their Saturday evening whirring around in an industrial-size tumble dryer. Emotions spun madly. From fear before kick-off, to mortification at those early England scores that landed with a thud on Scotland's already fragile demeanour, to anger at the concession of those 31 unanswered points in less than half an hour.
At that stage, Scotland were Ragball Rovers. They were a pub team, an embarrassing mess. They'd botched lineouts, they'd missed tackles, they'd kicked out on the full twice, they'd missed tackles that you would not expect an international team to miss. And they'd gone quiet, oh so quiet. Nobody was talking. Nobody was leading. To all the world it looked like they were going down with a whimper and not the bang they'd promised.
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England had 31 points on the board but they should have been closer to 40. England were slick, Scotland were slapstick. You would have bet your last fiver on them adding to their points mountain in the second half - 50, 60, maybe more.
The rollercoaster went on its merry way. A dread of the second half gave way to hope when Darcy Graham finished brilliantly seven minutes after the restart, and then excitement when Ali Price chipped and gathered and found Magnus Bradbury on a support run that no Englishman could see coming.
Two Scotland tries in three minutes. Three Scottish tries in eight minutes when you counted McInally's smash-and-grab off Owen Farrell just before the break. At 31-19, the Scots were beginning to regain some lost pride, but when Graham scored again - the key moment being Russell's sumptuous pass - Scottish eyes started to light up in a bewildering kind of joy.
It was 31-24 and then it was 31-31 when Russell, basking in the glory of a magnificent second-half performance, picked off Farrell's pass and ran away to score under the posts. Four tries in 20 minutes. Five tries in 25 minutes. What kind of madness was this?
Beery silence & smelling salts
The haplessness that belonged to Scotland was all England's now. Their own complacency had allowed the Scots back into it. Before long, complacency had led to panic. England found themselves in a dark, dark hole. Twickenham started to boo.
Farrell, enduring a nightmarish experience, was lucky not to have it ended by a yellow card after he drove his shoulder dangerously closely to Graham's head. It's something of a party piece of Farrell's. He didn't get 10 minutes but he got withdrawn soon after in any case. He made his way to his seat among the England substitutes muttering something when he got there. Whatever he said, it wouldn't have been kind - to himself or the shambles his team had become.
When Sam Johnson cut through the England defence to put Scotland ahead with five minutes left to play, it was hard to know what to do - applaud or faint. In standing up Elliot Daly and Jack Nowell and fending off Ben Spencer and George Ford, Johnson reduced the stadium's chattering classes to quivering wrecks.
One character behind the commentary seats - Twickenham Man from his top to his toe - fell into a beery silence where before he had whooped and hollered while demanding 100 points from his smooth-running heroes in white. As Johnson scored under the posts, the chap looked anaemic, a ghostly, less gobby figure all of a sudden.
It was a score that would have gone down in the annals had it been the final score, but of course, it wasn't. There was one last act, one concluding kick to Scotland's unmentionables. Those minutes, with 80 minutes on the clock, passed slowly.
A penalty at the breakdown, a kick to touch, a lineout rumble, a drive to the posts. Defence, defence and more defence. Stress and more stress. You could sense it coming, this cruel blow. Ford went through, then tapped over the conversion and that was that; 38-38. The rollercoaster returned to earth with some seriously shaken supporters on board.
Some colour returned to the cheeks of 'Twickenham Man', but he almost needed a hand out of his seat at the end. A stretcher wouldn't have gone amiss. Some smelling salts would have been useful.
Scotland's pride in what they did in the second half was deserved, as were the brutal words they used about the hopelessness of their first-half capitulation. They are a bizarre crew. Terrible and thrilling. Rotten and ruthless. The free-flowing, accurate, skilful and relentless 15 who came out for the second 40 minutes bore no resemblance to the useless lot of the first 40.
Why couldn't they play in the first half as they did in the second? How could they play with such fear and then such elan? Townsend's rugby knowledge is vast, but even he will be scratching his head at that one. He probably thought he'd seen it all - and then this near-miracle match unfolded. He'll need a rest now. After Saturday's whirlwind, he won't be alone in that.