>> hello, everyone, and welcome to a cnn special report, "mystery of flight 370." i'm don lemon. right now searchers are racing to confirm two pulse signals detected by a chinese ship. they were heard outside the search zone, but followed the same arc that has been guiding searchers. adding to the intrigue, they match the same frequency as a black box pinger. another acoustic event was also detected by the australian ship ocean shield about 300 miles away. searchers are now working on borrowed time, with the black box pingers quickly rung out of juice. that's if they're not dead already. and as the search continues, so does the speculation about what happened inside the cockpit. a senior source inside the malaysian military say the plane may have steered a mysterious course. for the very latest on the search, we're going to go to perth now, the hub of the search