Cool Stuff - things to make you go 'hummmm'

Detective Sara Dunts was called in for an investigation on a Saturday morning. Mr. John Gooding had mysteriously vanished from his one story home, Sara was told. "I'll phone Mrs. Glen, the caretaker, and get you the address." Detective Chad Sandlers, Sara's partner, said. Sara stood waiting as he made the call. "Okay, everything's set. Mrs. Glen will be expecting you in half an hour at 232 Parker At." Detective Chad said.

Sara hopped out of her car and walked up the long path that led to the house. Right away she was ushered inside by Mrs. Glen. "Detective, I'm so glad you came. The last place I saw Mr. Gooding was in his room. I suspected that would be your first question." Mrs. Glen said somewhat nervously. She walked Sara into the other room. "Up here," Mrs. Glen called from a twisting flight of stairs. The front door banged shut just as Sara started up the steps. "Oh, I must have left the door open. The wind must have shut it." Mrs. Glen said. Again they started up the stairs.

They walked up the enormous stairway. Halfway up detective Sara noticed a weather vane through the window. She realized that the wind was blowing west and in order for it to have shut the door it would have to have been blowing east. Then Sara realized for the first time that there was a third set of footsteps on the stairs. Then it dawned on her and she realized she had walked into a trap.

How did Sara know she had walked into a trap?