When Mortimer Henryson offers to take care of a strange plant called Plantzilla for the summer, he is in for more than he bargained for. In a series of letters a boy, his science teacher, and his parents discuss the progress of a very unusual, sometimes frightening, plant that becomes more human as the summer progresses.When Mortimer Henryson offers to take care of a strange plant called Plantzilla for the summer, he is in for more than he bargained for. In a series of letters a boy, his science teacher, and his parents discuss the progress of a very unusual, sometimes frightening, plant that becomes more human as the summer progresses.