What on Earth?

Something strange in the Himalayas could be evidence of a top-secret CIA programme to turn monks into killer agents; cutting-edge science helps experts investigate the truth behind the mysterious anomaly.

Alien monoliths haunt the coast of England; an obliterated jungle points to a brutal narco gold rush; evidence of a strange blood-red creature emerging from the deep.

A satanic symbol that points to an army of the dead in Siberia; a massive stone giant in a remote desert; evidence of a Russian doomsday device right on America's doorstep; cutting-edge technology helps experts answer sinister mysteries from space.

Zombie reindeer haunting the mountains of Norway; strange circles in the sand by a secret U.S. military base; a giant streak in the Arctic pointing towards alien life; cutting-edge technology helps experts answer these sinister mysteries from space.

A fleet of sunken ships that point to ghosts, cannibals, and bloodshed in early America; strange arctic holes that NASA can't explain; near Area 51, mysterious alien structures straight out of Star Wars.

New discoveries from space give experts new clues in the hunt for Jack the Ripper; a strange object crash-lands in Antarctica, experts speculate it could be an alien visitor.

Hundreds of shipwrecks in the middle of a desert in Africa; a ghost town where hundreds of its inhabitants have mysteriously died; something strange in North Korea; cutting-edge tech helps experts answer these sinister mysteries from space.

A site that could be the Garden of Eden hides a deadly secret; when a gateway to hell suddenly opens, experts investigate where it leads; a mysterious shipwreck could be an infamous Soviet KGB pirate ship.

Evidence of a mysterious 5,000-year-old structure suddenly appears in Ireland; a top-secret machine that can see back in time; a satanic pentagram in the snow that points to witchcraft in the New World.

A strange circular forest next to a notorious cannibal site; when an eerie crater is spotted in Siberia, experts uncover if it could be evidence of Nikola Tesla's doomsday device; cutting-edge tech helps experts answer these sinister mysteries.

Six breathtaking images, six unfathomable mysteries; from a possible smoke screen over North Korea, to two forgotten pyramids in Egypt.

Discover the link between Nazis in New Mexico and a mystery craft in Roswell, explore Australia's underground labyrinthine abyss and decode the cypher of Atomic Island. (S5, ep 19)