At first glance, this brain teaser seems like a simple description of five sisters in a room, each doing something different. However, the trick is hidden in the wording, as is common with many classic riddles that test attention to detail rather than complex logic.

Inside the room, there are five sisters present, and each one appears to be busy with her own activity. The situation looks complete, with no missing details or extra clues at first sight, which makes the puzzle seem straightforward.

Ann is reading a book quietly on her own. Margaret is in the kitchen area cooking. Kate is sitting down and playing a game of chess. Marie is occupied with doing laundry, handling chores around the room.

At this point, the question is asked: what is the fifth sister doing? Most people assume she must also have her own separate activity, since everyone else already seems busy and accounted for in the scene.

However, the key detail lies in understanding chess. Unlike reading, cooking, or laundry, chess is not a solo activity. It always requires two players facing each other and taking turns making moves on the board.

Since Kate is playing chess, she cannot be playing alone. A chess game requires an opponent, meaning another person in the room must be involved in the same activity with her.

This means the fifth sister is not doing something separate at all. Instead, she is the second player sitting across from Kate, actively participating in the chess game rather than performing a different task.

So, the answer is that the fifth sister is playing chess with Kate. The riddle works by hiding this obvious detail in plain sight, reminding us that careful reading and logical thinking often matter more than quick assumptions.