The "Silver City" of the title is Aberdeen, bustling capital of the North Sea oil industry. It is here that oil executive Hugh Donald is on trial for murder. Keith Calder, called as an expert witness, stuns the prosecution with some unexpected testimony and the result is a peculiarly Scottish verdict: Not Proven.
But Not Proven is a long way from Not Guilty, and Hugh Doanld - and his employers - are determined that his name be cleared. They persuade Calder to reinvestigate the crime. Following a trail of evidence several months old, Calder must unravel a deadly tangle of blackmail and corruption to find the real killer.