Christie Malry works in a bank, where he learns the principles of double entry book-keeping (i.e. for every debit there must be a credit.) For Christie, this explains his world: debit Christie for offence received, credit society for offence given. Christie opens his account with society and the reckoning begins, all accounts to be settled in full. His mother dies, he gets a girlfriend, the future looks bright. He starts to make the books balance with seemingly trivial acts of vandalism, but the clearer Christie sees the more he is owed and his actions escalate. Interwoven with Christie's experiences is the story of 15th century Italian priest Fra Luca Pacioli, who invented modern accounting. The rise of modern capitalism and artistic ideas in the Renaissance comes to provide a context for Christie's experiment in social accounting.