It is a tale of billions of pounds for schools, hospitals and transport projects.
At its heart is a question: if we leave the EU, will the cash dry up?
The answer lies with a little-known bank that commands vast resources.
Stand on the new tram stop in Exchange Square in Manchester and you can watch workers tear up concrete to lay tram lines.
Greater Manchester is set to receive half a billion pounds to help develop its tram system.
Walk away from the EU - say remain campaigners - and wave goodbye to fresh loans for schemes like this.
Not so, say the Leave side; there is nothing the European Investment Bank (EIB) does in its Luxembourg offices that the UK couldn't do for itself at home.
The EIB is handy for governments and councils because it helps pay for major projects, lends at cheap rates and guarantees those rates for years into the future.
It lent more than £5bn in the UK in 2015.
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No surprise then that it's a hit with some local politicians. Remain supporter and Labour leader of the City Council Sir Richard Leese says leaving the EU could put a stop to similar schemes in the years to come.
"That would mean in the future that if we needed to do something on this scale, and we undoubtedly will need to do more things on this sort of scale in Greater Manchester, it would make it very difficult, if not impossible, to do so in a way that gives good value for Council Tax payers," he says.
But the bank is just that: a bank, not a fairy godmother.
It doesn't magic money from thin air. Instead, it uses capital from EU members including more than £3bn of the UK's cash, alongside guarantees that it could demand much more from them, to borrow on the markets. Then it lends out the money to individual projects.
Mancunian and UKIP MEP for the area Steven Woolfe says there is no reason the UK couldn't create a British bank to do just the same thing if necessary.
Surveying a new tram stop, Woolfe says: "Richard Leese is wrong to suggest that big infrastructure projects, whether it's here or in other places in Europe, wouldn't get funded. It just wouldn't get funded by the EIB."
Where the bank makes loans to private companies, he says, it nationalises the risk of lending but privatises the profit; if a firm defaults EU taxpayers pick up the bill, if it prospers then shareholders benefit.
The bank's vice president Jonathan Taylor is a former British Treasury official. I ask him why the UK couldn't simply establish its own bank, on its own terms, under its own control.
He says: "Board members of institutions like mine, all of whom are nominated by the governments concerned and all of whom are accountable to those governments, will be making those decisions taking full account of what those governments want."
If the UK left the EU, current funding deals would continue but it would, he says, be "vanishingly unlikely" that the EIB would do the same scale of business in the UK as it does now.
David Cameron recently highlighted the EIB's work, including trains for the East Coast Main Line, the extension of the M8 motorway and new facilities at Oxford University. Alternative funding if we left, the PM said, would be unlikely.
At this, some Brexit campaigners roll their eyes. They believe the EIB is not merely a financing tool but a way of wielding the EU's power, letting it paint itself as a bountiful provider.
Yet on the new tram station partly funded by the EIB in central Manchester I could find no attempt to advertise its contribution. Unlike other arms of the EU, it doesn't make a habit of plastering its logo on projects.
Sir Richard accepts it's unlikely the passengers in Exchange Square have any idea of the EU bank's role.
With Britain's EU membership in the balance, it is hard to believe the Luxembourg financiers will get much of a PR bang for their not insubstantial buck.
This is a story of money and power.