Glasgow, 1957. It is a December night and William Watt is desperate. His family has been murdered and he needs to find out who killed them. He arrives at a bar to meet Peter Manuel, who claims he can get hold of the gun that was used. But Watt soon realises that this infamous criminal will not give up information easily. Inspired by true events, The Long Drop follows Watt and Manuel along back streets and into smoky pubs, and on to the courtroom where the murder trial takes place. Can Manuel really be trusted to tell the truth? And how far will Watt go to get what he wants?