Del's skint again and his latest deal has fallen through, but Rodney discovers a rare butterfly which will solve all of their financial problems.

A conversation with painter and decorator Brendan O'Shaughnessy leads to Del agreeing to supply enough louvre doors to refit an entire housing estate in Nunhead. Unfortunately, Del's mate Teddy Cummings can only supply in bulk - if the Trotters can't come up with the necessary £2,000 by the next day, they'll be out of the deal.

Just as they're resigned to losing out on the cash, a solution turns up in the form of Denzil's redundancy money; it's only once they've collected the doors that O'Shaughnessy says the estate's architect has changed his mind and no longer wants them! Albert suggests that they could just swap the doors for another kind, but Rodney's horrified when Del reveals that the entire stock is stolen, so there's no chance of that.

It's not long before Denzil's five brothers come looking for the money Del conned him out of, so with nowhere else to go, the Trotters visit their mother's grave - a favourite refuge for Del in times of trouble.

At their mother's graveside, Rodney notices a rare butterfly from the cover of his magazine, that's worth about £3,000 to collectors. After chasing the butterfly around the churchyard, the park and the boating lake, they finally capture it: only for Denzil to come by and unknowingly squash it.