Treasure Island
How did Ben Gunn know it would be safe for Jim to go to the stockade?
Treasure Island part 4
Treasure Island part 4
Ben Gunn knew it was safe because the British flag is clearly a signal of where his friends are, and because the pirates would never fly a British flag, but instead a Jolly Roger. After pointing Jim in the right direction, he declines to join him but instead will be available at any time to discuss plans with the doctor or the squire.
http://www.gradesaver.com/treasure-island/study-guide/summary-chapters-14-20