H.G. Wells, having invented the time machine, decides to visit the United States in 1849. Eventually he ends up in San Francisco, California.
While walking to the saloon, he is suddenly dragged into an alley by several strong men. Surprised and terrified, he doesn't even have time to yell. He is even more surprised when one of the men exclaims, "Here! Take this! We don't want no part of this!", and shoves something large and heavy into his hands. The men then run away. He is even more surprised when he looks into his hands and sees the largest gold nugget he has ever encountered. It is as big as his fist, and worth several thousand dollars.
After pocketing the gold, he starts toward the saloon, but then has an idea. Instead of continuing, he turns around and heads for the basement of the barn where he has hidden his time machine.
He gets into the time machine and sets it for two weeks prior to his arrival. Through careful observation, he finds the three men that accosted him in the alley. After donning a fearsome disguise (a "Friday the 13th" outfit he aquired on a trip to the 20th century), he appears to them in his time machine late at night, when they are heading back to their prospecting camp after a night of drinking and gambling.
The men are, of course stunned speechless. He gets out and gives one of the men the giant gold nugget that they had given him previously. He gives them a picture of himself (without the disguise) and tells them that at noon tomorrow the man in the picture will be walking past that (points) alley. They are to give this man this piece of gold. If they fail to give it to this man, terrible things will happen to them. Terrified beyond belief, they can only nod their assent.
Wells gets into his time machine and disappears, but only a few hours into the future. He carefully observes the men to ensure they do in fact give this nugget to the Wells walking down to the saloon the next day. Satisfied, he sets his time machine to his own era and returns home to London.