Cat and Mouse

A shocking online video brings together a widespread internet group of animal lovers out for justice. Their target, meanwhile, has more horrors planned.

Killing for Clicks

A new video pushes panic to the next level, galvanizing the "internet nerds" to intensify their own painstaking investigation as police join the hunt.

Closing the Net

With the killer's identity -- and twisted motives -- revealed, the group finds more key clues as the global police manhunt reaches a fever pitch.