It's the mystery of tens of thousands of pounds worth of bank notes found floating down a river.
An unsuspecting member of the public was walking their dog, alongside South Drove Drain, near Spalding, when they spotted the cash.
A staggering £60,000 has already been recovered from the waterway, and there's even been suggestions that there could be even more still in the river.
Some of the recovered money is water damaged and some appears to have been partially burned. However, much is still usable.
Speaking to ITV News Anglia, Detective Inspector Steve Hull from Lincolnshire Police, says that no one has yet come to claim it.
Meanwhile in the pubs and the cafe's of Spalding there's plenty of talk about the cash, and about what people would do if they found that kind of money.
The courts have now given the police six months to establish where the money comes from and who, if anyone, is entitled to get it back.
If it does turn out to be criminal it will be permanently confiscated. Although the finder could still get a reward.
Detectives are warning anyone who comes to claim it that they'd better have a very good explanation.
And they're already getting tired of jokes about money laundering.