The only way to answer the questions about why crime falls, he says, would be to build a wall around each county in the UK, and then change the conditions to establish the influencing factors.
They go to a lonely country house, inhabited by a pair of wealthy oddballs called Flower (Charles Durning) and Stone (Joel Grey), who trounce Pozzi at poker and then demand an unusual repayment: he and Nashe must build a stone wall in the grounds.