assassination of president kennedy and the death of marilyn monroe. we have more on the conspiracy theories linked to the biggest uninvolved mysteries. >> even when there are plausible explanations. >> like the bobby kennedy case, like amelia earhart. >> reporter: the answers don't always satisfy. >> i think mysteries mean questions. the strait of gibb brawl tar, 100 years ago, what happened to the crew, pirates, perhaps a sea monster. all popular theories debunked in this 2007 documentary, which tells us what didn't happen but doesn't tell us what did. 77 years after amelia earhart disappeared during her trip around the world, the search continues. wreckage has never been found. and los angeles county where new questions have come to light about the long-debated death of