and on all the second, five weeks after lauren disappeared, stephen mcdaniel, the quiet young law school. then, really of a crime so awful, a dismembered victim. we stephen head seems so harmless. no criminal record. the evidence against him with circumstantial. the district attorney wasn't confident. >> i was worried that unless we had more, that this was a case where everybody knew that he did it, but nobody could prove it. >> so, time to take a harder look at the evidence. >> coming up. investigators are about to discover a certain piece of deleted video. >> what was it like to see that? >> i knew we had him. >> do they though? when dateline continues. with less moderate-to-severe eczema, you can roll up those sleeves. with dupixent, teens saw clearer skin and significantly less itch. don't use if you're allergic to dupixent. serious allergic reactions can occur including anaphylaxis, which is severe. tell your doctor about new or worsening eye problems, such as eye pain or vision changes or a parasitic infection. if you take asthma medicines, don't change or stop them without talking