Three aging sisters were living together.  One day one of the sisters went upstairs and decided she would have a bath.  She had just put one foot in the tub when she became quite upset and called for help from her other two sisters.  She called out , “I can’t remember if I was getting in the tub or getting out of the tub!”  The second sister called  out that she was coming.  The second sister got only half way up the stairs and she called to the third sister who was sitting at the table that she couldn’t remember if she was going up the stairs or down the stairs.  The third sister called out saying “good heavens!  I am glad I’m not gone senile like the two of you,  knock on wood “!  She knocked on the table as she spoke.  Then she said “Oh wait a minute!  Someone is at the door”!