A routine expedition on a hillside in the badlands of South Dakota, lead a paleontologist to an amazing discovery. The mummified tail of Edmontosaurus, a duckbilled dinosaur is uncovered with evidence of a vicious attack--tiny serrated teeth are found and linked to Dromaeosaurus; members of the raptor family. However, the bones also reveal evidence of a second attacker--Tyrannosaurus Rex. Watch as experts recreate the events leading up to the slaughter of Edmontosaurus, revealing a predatory world far more calculated--and complex--than we originally thought.