A Brainteaser For You

Every fall the Ace Hotel saw the pilgrimage of the Blue
Society in their quest to watch the leaves change color.
They counted their nickels and drank large quanties of tea,
but otherwise, were no trouble except for this year. One of
their members was a thief. Hotel rooms were invaded and
wallets were stolen. Then the hotel called in a detective.
The detective ordered dinner in his room where he could
devise a plan of capture. First, the maid came in to deliver
fresh towels. Then a newlywed couple, locked in embrace,
accidentially entered his room before making an apologetic
departure. Next, an elderly lady knocked and entered, then
apologized when she saw it was the detective's room and not
hers. Then room service knocked bringing in the detective's
dinner. Half-way through dinner he suddenly knew who the
prime suspect was. Who?


SOLUTION:
It was the elderly lady. If she had really thought it was
her room, she wouldn't have knocked before entering.