It is past midnight when two callers come knocking at the London flat of down-and-out, long-out-of-work Peter Diamond. When they turn out to be two CID men from his former police division of Avon and Somerset, he's baffled. When they order him to accompany them, he's mad as hell at being rousted from his warm bed - and intrigued. When it turns out his old department has an emergency only he can handle, he can barely stop himself from saying "I told...