The Silver Tombstone

When Johnny Fletcher and Sam Cragg's jalopy runs out of petrol, a Samaritan by the name of Joe Cotter pushes them to a motel and demands twenty dollars. Early the next morning, they siphon petrol from Cotter's convertible and make a hasty exit. However, they quickly dump their car when they discover a dead body sprawled in the back seat. They hitch a lift to Los Angeles, where a silver nugget comes hurtling through their hotel window. Is there a connection between this and the dead body?