Brian Dickinson has always been an adventurer, and was Air Rescue Swimmer in the Navy, and is now a very accomplished mountaineer.

He's written a book about his climb of Everest called "Blind Descent: Surviving Alone and Blind on Mount Everest." Today he tells Mark about how he got into mountaineering after the Navy, and his harrowing adventures climbing Everest.

Hear how: He lost his Sherpa to illness with about 1000 feet left to go to the summit The day after summiting, he lost his ability to see, and had to make his way down without eyesight.

An oxygen tank that had malfunctioned earlier miraculously started working just in time for him to be able to breath Understand how faith and determination allowed Brian to overcome one of the most difficult situations imaginable.