What can explain the grisly deaths of nine students who went missing in Siberia? New investigation of declassified Soviet files reveals evidence of their horrifying ordeal, and scientists examine clues that may prove the existence of a yeti.

Alien Skull: In Peru a tiny skeleton resists medical explanation. Is it a missing link in human evolution? Or proof of extra-terrestrial contact? Baltic Sea Anomaly: Wreck detectives ind a huge disc twice the size of a football field on the seabed.