Not many days after the soup incident, the narrator says that something worse happened to Billy. He was sleeping in the upper deck one night and was awakened by someone, who told Billy to go meet him in another part of the ship. As Billy was not the sort of person to say no to any request, he went to meet with the unknown man.
It is not in Billy's nature to say no to the request of a fellow shipmate. However, any loyalty owed to this unknown comrade has a limit, as we will see when he asks Billy to go against his loyalty to Captain Vere.
Billy went to meet the man, whom he did not recognize in the dark. The man told Billy that there were a large number of sailors on-board who had been conscripted into service. He asked Billy, "Couldn't you—help—at a pinch?" Billy asked what he meant and the stranger offered him two guineas, though it is unclear what exactly he was asking for.
While it's never explicitly stated, the unnamed man here seems to be hinting that he wants Billy's help in planning a mutiny, and seeks to gain Billy's comradeship by explaining that he and other share a past with Billy—they've all been forced to join the navy. In essence, the man is suggesting that those forced to give up their individual rights to join the navy should forcibly reassert those rights through mutiny. By offering Billy money, he encourages Billy to value his own prosperity above the well-being of the ship as a whole.
Billy refused the coins and told the stranger to go back to his post, or else he'd throw him overboard, stuttering in his nervousness. Another sailor, awakened by the ruckus, asked Billy what was going on. Billy said he simply found someone away from his post and told him to return to his proper area.
Billy remains loyal to his captain and ship by returning the coin and threatening to throw the other soldier overboard. Yet he also shows his camaraderie to that same sailor by making up a lie and not turning him in. Billy stands right in the middle of the tension between loyalty to captain and camaraderie with his fellow sailors. Incidentally, it's worth pointing out that it is never clear whether this is another "test" from Claggart or whether the mystery sailor really is trying to put together a mutiny. This scene further establishes Billy's stutter, which will come into play later.
Another awakened sailor nicknamed Red Pepper doubted Billy's story and said he'd like to punish Billy and whomever he was talking to. However, the surrounding sailors believed Billy's story because, as the narrator notes, sailors are particularly annoyed when people are not in their proper, assigned places and so sympathized with Billy reprimanding the other sailor.
Red Pepper exemplifies the naval habit of swift punishment for any infractions. However, the other sailors are sympathetic to Billy because of the importance placed on every sailor's specific duties aboard the ship—in the fact that all sailors depend on the others for their survival. Camaraderie between the men therefore arises from the fact that they all hold each other's lives in each other's hands.