In Treasure Island," the receipt by Dr. Livesey and Jim of the Squire's letter from Bristol gave three significant clues to impending danger and rough seas ahead. Stevenson writes these so masterfully that the reader senses at once the "Uh-oh!" quality of the Squire's statements. The first clue pertains to the Squire himself. Dr. Livesey said that the Squire was the one whom he feared because he couldn't keep a secret to himself. The Squire agreed saying that the Dr. had spoken rightly. And in fact, it turns out that the Dr. was right: the Squire did let the whole city of Bristol know that they were after treasure. Trouble, my friend.
It is significant to note that the other two clues depend on the Squire's indiscretion of telling their secret. The second clue pertains to how the Squire met Long John Silver: Long John just happened to turn up--oh, yeah, uh huh.: "fortune brought me the very man that I required. ... I was standing on the dock, when, by the merest accident, I fell in talk with him." By the merest chance occurrence Long John just happened to be there after the whole town had been a-buzz with talk of treasure.
The third clue stems from both the second and the first. Long John Silver gathers the Squire a crew of the "toughest old salts imaginable" who are fearsome to look at, with the "most indomitable spirit," and who "could fight a frigate." (A frigate is a fast naval vessel that is high masted and heavily armed with cannons on two decks! Random House Dictionary, Dictionary.com.)
These are the three clues, and they make an attentive reader's hair stand on end just thinking of the trouble or it makes the incredulous reader say, "The Squire what? He wouldn't have. He couldn't have. Oh no, he did!"