David Attenborough returns to the island of Madagascar on a very personal quest. In 1960 he visited the island to film one of his first ever wildlife series, Zoo Quest. Whilst he was there, he acquired a giant egg. It was the egg of an extinct bird known as the 'elephant bird' - the largest bird that ever lived. It has been one of his most treasured possessions ever since. Fifty years older, he now returns to the island to find out more about this amazing creature and to see how the island has changed. Could the elephant bird's fate provide lessons that may help protect Madagascar's remaining wildlife? Using Zoo Quest archive and specially shot location footage, this film follows David as he revisits scenes from his youth and meets people at the front line of wildlife protection. On his return, scientists at Oxford University are able to reveal for the first time how old David's egg actually is - and what that might tell us about the legendary elephant bird.