When Patty comes to visit her aunt, she is poisoned by arsenic in the water. Her aunt finds the source of the poison in an old mine but is trapped when the floor collapses. Lassie helps the aunt by finding Patty before she leaves for home.
Patty comes to the country to visit her aunt then is poisoned by arsenic in the water. Her aunt finds the source of the poisoning in an old mine but is trapped when the floor collapses. Lassie must find Patty before she returns to the city.