Mary must find a perfect shamrock in Manhattan in the middle of winter…. In 1849, after several years of failed crops in Ireland, Mr. McLean and his wife packed up their family and headed to America. Once there, they settled in New York, in an area with a lot of other Irish immigrants. Mary hears vague stories about what Mr. Finnegan does each year for the St. Patrick's Day parade and, when she asks for details, learns that he drives a cart pulled by two white horses and looks like an Irish hero. Mary would really like to ride in Mr. Finnegan's cart. When she asks him, Mr. Finnegan says it's possible - but she'll have to bring him a perfect shamrock... IF she can find one!