In the beginning of the story, Duffy, Aunt Elise, Marie, Andrew, and Andrew's mother are on their way to the cabin. The cabin is located in the middle of nowhere, and is surrounded by forest. Andrew's cousin Duffy has been introduced as a very forgetful being.
Eventually, Andrew and the others have arrived at the cabin and found it isn't as beautiful on the inside as they thought it would be. They have found that the cabin is run down and battered.
As the children were cleaning the house, they found a message written on the wall that read, "BEWARE THE SENTINEL". Afterwards, Andrews mother and aunt Elise thought that it was a joke, and were mad at Andrew for frightening Marie.
BEWARE THE SENTINEL
Soon after, the kids decide to go for a walk in the forest. It was fairly hot, so they had decided to take of their jackets. When they had returned they realized that Duffy had left his jacket. Andrew had told his mom that he felt someone was following them while they were in the woods; she then accused Andrew of trying to ruin the trip. The two mothers then began to get ready to leave and to go to town.
By the time the two mothers had left, the children had heard scratching noises on the door. Duffy had checked the door, and saw there was indeed something there. The thing had found them by Duffy's jacket. They had ran everywhere from the kitchen, to the barn. In due time, they ran upstairs locking the front door behind them.
After they had hid themselves in a room, the children were hunched against the wall. They then heard a terrible crashing sound. The Sentinel had broken down the front door. The Sentinel became to climb up the stairs; it had reached the outside of the door. The Sentinel entered the room and spoke, "You forgot your jacket, stupid." In the end, the children are all safe. and Duffy has his jacket. Not to mention, Duffy doesn't forget things anymore.