When Johann Lamont, Ruth Davidson and Willie Rennie stood outside Edinburgh's Dynamic Earth yesterday to announce a "delivery plan", you half expected to be asked if anyone would be in between nine and 12 a week on Thursday to sign for the package.

In that event, I wouldn't make too many plans. The box is empty. Or rather, there's a great deal of wrapping around nothing very much. At the bottom of this gift from the parties of the Union to the voters of Scotland there is just a timetable, of sorts. The parties swear, hands on hearts, that it is utterly reliable.

The assertion provoked a few questions from the media assembled in the shadow of Arthur's Seat. Wasn't the sudden appearance of this party gift bag so very late in the day a sure sign of panic in the Better Together ranks? Why didn't the Unionist parties make this move months and years ago? What was the great announcement, in any case, if not a mere restatement of promises made previously?

The questions continued. Why, even now, could Labour, the Tories and the Liberal Democrats not come up with a unified offer? How could voters be sure that the timetable would not be binned in the event of a No as, we can be sure, general election fever again took hold at Westminster?

A few more questions could have been added. The plan of action presented by Gordon Brown, the backbench MP suddenly behaving as if he's Prime Minister again, is ambitious, to put it kindly, if only in its audacity. A White Paper is promised by St Andrew's Day and a draft bill by Burns' Night. Forget the patronisingly daft choice of dates and the usual pledge to "consult": is that even feasible when the three parties cannot agree on basic points?

Already there are mutterings from constitutional lawyers in Westminster and beyond. They reckon that "more powers" for Holyrood is a gesture with implications across the UK. They see a piece of major legislation requiring lots of the usual pondering. The idea that anything of the kind should be rushed through just because Labour is bleeding support in the referendum campaign is anathema. The sage types make an excellent point.

Voters might meanwhile question whether any of the Westminster parties will find reforms, whatever they might be, so desperately urgent once a No vote is in the bag. The Commons does not overflow with English Tories sympathetic to Scottish claims. None of the three parties, Labour in particular, has yielded ground on the powers that might be granted. And the objection sticks: why did no one in Better Together think any of this was vital before an opinion poll detected the rising tide of support for a Yes vote?

The permutations can be done in any way you like, but the things missing from Scotland's lucky bag are easy to list. Under no circumstances would a devolved Holyrood get a sniff of power over corporation tax, the instrument - or so Mr Brown used to say when he was cutting the thing - of job creation. Edinburgh would not be allowed near VAT. Labour is determined to withhold complete control over income tax. As for North Sea revenues, those symbols of Scotland's wealth: don't even think about it.

Even by the standards of Better Together, this is a mess. Amid the self-evident panic there is, too, a familiar arrogance towards voters. "Tell them something," says the hard-pressed strategist, "tell them anything." Above all, as George Osborne contrived while being interviewed by Andrew Marr at the weekend, tell the simple folk that repackaged old goods are new and irresistible.

The Chancellor, like Better Together generally, was naughty. The Scottish Referendum Act decrees that, in the 28 days before polling, neither of the governments party to the Edinburgh Agreement should publish new information intended to support one outcome or another, or information dealing with the referendum question, or information supporting arguments for one side or the other. So what was Mr Osborne up to? What was the unveiling of the "delivery date" if not a breach of this "purdah"?

Downing Street has a bland if flagrantly dishonest answer to that. Mr Osborne, a government minister, breached no rules, a spokesman said. The offer comes from "pro-Union parties, not the UK government". Like it or lump it. Two of the parties making the incoherent offer happen to form the government in question, but the hair has been split, at least to the satisfaction of those bending the rules. Downing Street is meanwhile "content" - you bet - with Mr Brown's statements.

You could wonder if it matters, especially when the Better Together parties - not to mention the UK government - are floundering to stem the tide of Yes. That would miss the point. Some 200,000 postal votes were reported as returned before Mr Osborne spoke, before Mr Brown returned like Labour's Cincinnatus, and before three Scottish leaders found themselves grilled by the media. Those 200,000 voters knew nothing about any "fast-track plan" for still another devolution scheme. Whether you incline to Yes or No, that's wrong.

No one involved on the Union side - Jim Murphy, Douglas Alexander, Mr Brown himself - has bothered to do more than brush the issue aside. Had Yes Scotland been involved in such a swindle you would have heard the uproar all the way from Kirkcaldy to Westminster. When the sleight of hand is done in the sacred cause of the UK, however, we are told to look the other way.

First David Cameron insisted there could only be a "straight choice", Yes or No. Now, desperate, he and his bedfellows would have you believe that a rejection of independence leads finally to the elusive "devomax". Even that isn't remotely true. Nevertheless, 200,000 people are entitled to ask, "What did I just vote for?"

This is Better Together's last throw of the dice. The wailing calls of London commentators for that fabled positive case are irrelevant now. It was promised time and again and it failed to materialise. Revealingly, crushingly, none of the politicians charged with saving the UK has managed more than Mr Cameron's twee protestations of love for the Scots who decline to grant him more than one MP. Ed Miliband meanwhile asks for the Saltire to be hoisted above England's cities and towns. Perhaps he thinks people have forgotten what it looks like.

Both men will appear in Scotland today, as though to defy their miserable popularity ratings. English and Welsh Labour MPs are on their way too, to stiffen spines. But the telling statement on the state of the UK will be an act of omission: England's Tory MPs will stay away, as instructed. Having them in these parts might remind Scots of what being British means. That, reasons Better Together, will never do.

Instead, it is Mr Brown's job to shepherd former Scottish Labour voters back into the fold. While Coalition politicians keep profiles lower than the horizon, the former Prime Minister is supposed to save the Union. Along the way, he might ask himself why the Labour vote strayed to begin with.