until you find the plane, how can you rule anybody, anything out? >> well, you can't. what you'll know from the black boxes is what happened. what you won't know necessarily is why. >> there are no black boxes inside human beings. that's what we need in this case. >> our best hope of solving one of the greatest mysteries of all-time, presumably still lies somewhere at the bottom of the indian ocean. >> we need to know what happened. we need to know whether this plane came down at the point of a gun, by the hand of the pilot, or mechanical failure. it is not an option not to know. coming up, a brand new search for answers begins in the indian ocean. >> it's a big, big hunk of ocean. it's as remote as you can get as still be on the planet.