is a television series on the Discovery Channel and History (Canada) hosted by William Shatner (except for the U.S. version of Season 1, where his segments were replaced by a fourth story).

As the show unfolds, it weighs various supernatural and scientific theories that attempt to explain the story, and sometimes features tests conducted as proof of a theory's plausibility.

The show features phenomena such as ghosts, aliens, monsters, medical oddities and natural disasters.

[1] The U.S. version of season 1 of the show features four stories per episode.

The version generally shown outside of the U.S. features three stories per episode, in a different order and is hosted by William Shatner.