Willy is a killer whale who was taken from the sea at a very young age and kept at the North West Adventure Park to entertain visitors. When Jesse, an unhappy 11-year-old boy with no home or family meets Willy, he knows he has to save him. "Penguin Readers" is a series of simplified novels, film novelizations and original titles that introduce students at all levels to the pleasures of reading in English. Originally designed for teaching English as a foreign language, the series' combination of high interest level and low reading age makes it suitable for both English-speaking teenagers with limited reading skills and students of English as a second language. Many titles in the series also provide access to the pre-20th century literature strands of the National Curriculum English Orders. "Penguin Readers" are graded at seven levels of difficulty, from "Easystarts" with a 200-word vocabulary, to Level 6 (Advanced) with a 3000-word vocabulary. In addition, titles fall into one of three sub-categories: "Contemporary", "Classics" or "Originals". At the end of each book there is a section of enjoyable exercises focusing on vocabulary building, comprehension, discussion and writing.
Some titles in the series are available with an accompanying audio cassette, or in a book and cassette pack. Additionally, selected titles have free accompanying "Penguin Readers Factsheets" which provide stimulating exercise material for students, as well as suggestions for teachers on how to exploit the Readers in class.