Death Eaters ambush Harry, Ron and Hermione in the Forbidden Forest and take them captive. After taunting them and taking their wands, Voldemort gives them one chance to escape with their lives.

The trio are lined up in order of height and are tied to trees. Ron, who is at the back, can see the backs of his two friends. Harry, who is in the middle, can see Hermione’s back, and Hermione cannot see anyone. The Death Eaters show the trio five hats. Three of the hats are purple and two of the hats are black.

Blindfolds are then placed over each of their eyes and a hat is placed on each of their head. The two hats left over are hidden. The blindfolds are then removed and Voldemort tells them that if one of them can guess what colour hat they are wearing, they are all free to leave.

Ron, who can see both of his friends’ hats but not his own, says, “I don’t know”. Harry, who can see Hermione’s hat, but not his own says, “I don’t know”. Hermione, who cannot see anybody’s hat says “I know!”

How did she know the colour of her hat and what colour was it?

HINT: It’s not because she’s super clever and the other two aren’t!