A few days after the soup incident, Billy has gone to sleep on the upper deck because it's incredibly hot below deck. As a foretopman, this is his right and so no one blinks an eye.
He's awoken by a stranger, one of the afterguard, who tells Billy to meet him on a narrow private platform hanging out over the sea.
Billy, being good-natured as he is, dumbly goes to meet him there.
The afterguard tells him that there's a group of the men who are impressed, meaning to say disappointed, and ready to mutiny against the Captain of the ship.
He asks, "Couldn't – you – help – at a pinch?" (14.7). He offers Billy two guineas.
Billy becomes incredibly angry and his stutter sets in so violently that he can barely get his words out. He tells the afterguard to get away from him or he'll throw him over the side of the boat.
The afterguard scrams.
The other forecastlemen (men who patrol the top deck) wake up and, hearing Billy's stutter, they know that something was wrong.
He tells them that an afterguard was on top deck where he was not supposed to be, and that he told him to go down below. They think he should have been harsher with the afterguard, but let Billy's explanation stand because forecastlemen tend to despise afterguards.