Three widely separated households – one in Scotland, one in the north of England and one in the south – have known the pain of losing a loved one; losses which, over the years, have shaped the characters of those left behind. But it takes the untimely and suspicious death of Martin Petrie, a stranger from the Scottish Borders mowed down in a hit and run, to untangle the threads that will draw them together in ways they could never have imagined, with results that are far-reaching – and fatal.