William Shatner shares the formative influences on his path, and the lessons learned that informed a great career that shows no signs of slowing. That started when he was a young actor who played a small part and understudied Christopher Plummer in ‘Henry V.’ When ‘The Sound of Music’ star turned up ailing, Shatner stepped in and crushed the role and learned a lesson that sustained him: it is best to succeed or fail on your own terms.