Who killed Kim Jong Un's half-brother, Kim Jong Nam, and what does the murder reveal about the North Korean leader and his intentions and his regime and its capabilities?

"Mosul" and "Inside Yemen" are both in this two-part hour per Frontline website.

"Mosul" - Described by some military commanders as the deadliest urban combat since World War II, the battle to drive ISIS out of Mosul, Iraq was brutal and grueling. Shot over the course of the nine-month battle, "Mosul" follows four young Iraqi special forces soldiers tasked with leading the fight.

"Inside Yemen" - An up-close look at how Yemen's humanitarian crisis was worsened by a brutal war.