Show #58 (season 5, edition 4)

Debut: FRIDAY, MARCH 17 (7:30-8:00 p.m. ET/PT)

"Kings of Cannabis": The legal marijuana industry is set to surpass $20 billion globally by 2020. At the heart of this "green boom" are strain hunters, who search the Earth's far corners for never-before-mixed strains of marijuana known as "landraces." Correspondent Hamilton Morris joins two hunters on an epic journey through the Democratic Republic of Congo in search of one of the rarest species of cannabis, whose unique genetics could ultimately earn them millions of dollars.

"Into the Darkness": According to scientists, if you gathered up every physical thing we can see in outer space - the Earth, all the planets, all the stars - it would account for a mere 5% of the Universe's total mass. The other 95% is known only as "Dark Matter" and "Dark Energy," and understanding these two forces is the biggest mystery in modern physics. From an abandoned gold mine a mile beneath the Black Hills of South Dakota, to the world's most powerful telescope nestled into the high deserts of Chile, nuclear physicist Taylor Wilson meets the scientists working to unlock the secrets of the Universe.