Transit of saturn

Dear Friends,
I am narrating a funny story(is it funny?) told by Thenkachi Swaminathan a few days back:-
One man got married to a girl. On the day of the marriage they visited the temple. While they were talking and walking in the temple, a stone which was protruding on the temple flooor hit the wife's feet and she had to sit down. The husband was terribly perturbed and told"That stone is a saturn.Why should it protrude and cause you pain, darling?" after a few minutes they left the temple.
After many years the same husband and wife along with their four year old daughter visited the same temple and the same stone hit the feet of the same wife. The same husband told, "Hey Saturn like girl, Can not you see that Mummy is hurt. Had you not been naughty, poor mummy would not have hurt her feet.Sorry my wife."After a few minutes, they left the temple.
After many more years, the same husband and wife along with the same daughter visited the same temple. The same stone hit the same leg of the same wife.The husband addressed his wife, "Hey saturn, ca'nt you see down while walking. You have unnecessarily caused yourself a wound.Who will pay the doctor's bill-your father.". The husband walked away fast and disappeared.
What is the cause of the transit of saturn from the stone, to the baby daughter to the wife.Normally saturn changes once in every 30 months. But in this case, what is the normal period? Ramachander