What occurs at night at the stockade?

I'll assume that you mean what happens at the stockade in relation to Jim Hawkins, the main character and primary narrator of the exciting novel Treasure Island by Robert Louis Stevenson. Jim is involved in two important events on two different nights at the stockade.
The first instance happens after Jim has joined Long John Silver and some others on a shore party, shortly after they arrive at the island. After witnessing Silver murder an innocent sailor, Jim flees and comes across old Ben Gunn, who was marooned on the island when pirates buried treasure there. After leaving Gunn, Jim finds the stockade, climbs in, and discovers Captain Smollett, Squire Trelawney, Dr. Livesey, and others from the ship waiting for him. In the morning, Silver negotiates for the treasure map under a flag of truce, and when he doesn't get what he wants, the pirates begin an attack on the stockade.
Another incident occurs the next day. Jim runs off without permission, takes Gunn's boat out to the ship, and, despite a pirate injuring him, manages to beach the ship. When the wounded Jim returns to the dark stockade at night, thinking that his friends are there, he finds out too late that the pirates have taken over the stockade, and they capture him. Some of the pirates want to kill Jim, but Silver protects him. In the morning, Silver and the other pirates take Jim with them as they search for the treasure.