An unexpected visitor arrives at the front door. He is an anonymous man in a grey suit carrying a clipboard. His presence is enough to turn a happy family scene into one of anxiety and anger. Dad tells the family: "He's just told us he's cutting our tax credit." Mum complains: "It's not fair."
That is the start of Labour's latest election broadcast which warns of the cuts the Tories are planning for families.
It is evidence, ahead of tonight's third and final prime-ministerial debate, that despite whichever party is elected, Gordon Brown still believes that fear of Tory cuts is still a major vote-winner.
He does so with good reason.
Ever since John Major's surprise election triumph over Neil Kinnock in 1992 - a defeat burned into Gordon Brown's psyche - election campaigns have been dominated by parties costing each others' tax and spending plans.
Ever since, politicians on all sides have tried to ape the success of the Tory poster which warned of Labour's tax bombshell.
Ever since, they have feared spelling out the cost of their plans as Labour's then shadow chancellor John Smith did with disastrous consequences in his shadow Budget in 1992.
That is why the prime minister refused again and again to use the "C-word" - cuts - until forced to do so by media pressure and cabinet insistence.
That is why David Cameron insisted for month after month that he would match Labour's spending plans, not change them. When he changed that position and spoke instead of an "age of austerity" and spelt out cuts in pensions, pay and tax credits his poll ratings fell and he abandoned his rhetoric.
That is why Nick Clegg dumped his warnings of "savage cuts".
It would, however, be a mistake to say, after the IFS's report, that all parties are the same and that there's nothing to choose between their pre-election offers. Here's my attempt to summarise the differences, in advance of this evening's prime-ministerial debate on the economy:
The scale of cuts
Gordon Brown believes that lower-than-feared unemployment and higher-than-expected tax revenues mean that the IFS is unduly pessimistic about the public finances. He argues that low interest rates and inflation make faster economic growth than many economic forecasters expect is possible.
Both the Tories and the Lib Dems believe that he is understating the scale of the task.
The timing
The Tories insist that "making a start" to reducing our borrowing by cutting £6bn from public spending this year is vital.
Labour and the Lib Dems will warn that this risks recovery and that if any efficiency savings can be made this year, they should be reinvested into more worthwhile government spending.
The balance between higher taxes and lower spending
The Tories say that international evidence shows that spending cuts should take more of the burden of cutting the deficit than Labour plans.
The Lib Dems agree with the Tories that bigger spending cuts are needed. Their plans are complicated by proposals for a huge tax cut - costing £17bn - paid for, they claim, by closing tax loopholes, limiting tax avoidance, increasing taxes on expensive houses, pension contributions and flying.
Who's been most honest
Gordon Brown says he deserves credit for unveiling unpopular tax rises before an election and that the Treasury has set out a plan to cut spending but that it was unwise to carry out a spending round during a period of uncertainty - you can't, he says, do a weather forecast during a hurricane.
The IFS is unconvinced, pointing out that there will be uncertainty on the other side of the election as well as before it. The Tories and the Lib Dems point out that there is a big difference between setting goals for spending cuts and taking the tough decisions needed, let alone spelling them out before an election.
The Tories have the biggest gap between the spending cuts they need to make and the detail they've given. This is because, as well as promising to cut the deficit faster, they are offering to limit tax rises and to protect spending on the NHS and international aid - what I have called a three-card trick.
The IFS says the Lib Dems have been least bad. They have, though, also faced the least scrutiny over the impact of their tax plans.
What should be cut? Which tax should be raised?
This is the debate with which we are most familiar and which most voters find easiest to follow without the help of the IFS, Stephanie Flanders and a computer spreadsheet.
Gordon Brown wants voters to focus on what he says are the Tories' priorities - cutting inheritance tax instead of protecting child tax credits and stopping the rise in National Insurance instead of protecting school spending.
David Cameron wants them to think about whether they prefer a tax cut to continued wasteful government spending.
Nick Clegg will insist that he can cut ordinary people's taxes and cut the deficit and increase school spending.
So, there are important choices facing the family portrayed in that election broadcast. However, that metaphorical man with the clipboard will be coming round asking them to pay more tax, get lower pay and pensions if they work in the public sector and cutting spending on things they value, whoever they vote for.