From John Le Carre's Smiley's People:
At a crucial moment, an unknown man turned round and looked at me and I hung an entire history on him, even imagining he was my dying father.
Background: "I" refer to the young man acting as a courier for the general. The "unknown man" was sent by the general to get the picture and deliver that via the young man.
My understanding was that the picture was so important that it might alter history, which depended on that unknown man.
The young man ("I")says that when he first saw the "unknown man" he imagined a complete past history (life story) for him. The pronouns I and him make it clear who is doing the "hanging".
The unknown man, who we will later learn is named Otto Leipzig, has a striking appearance that gives him a sort of aura of mystery. (Madame Ostrakova gives him the nickname “the Magician.”) He exchanges this look with Max, and Max is inspired to imagine a background story for this mysterious man.
(There are several places in the Smiley novels where perception and imagination set the spies apart from ordinary people, and this is one of them.)
