From the Ukrainian frontlines to the mines of the Central African Republic, this week's Four Corners lifts the veil on Putin's private army – The Wagner Group.In this independent French television investigation, former senior Wagner insiders speak out about what they saw in the line of duty.The film traces the group, from its origins in Ukraine, to its clandestine operations in Syria, and its reign of terror across Africa where victims tell of rape, torture and massacres.It also follows the rise and fall of the group's leader Yevgeny Prigozhin who recently dared to challenge Putin's power by marching on Moscow with thousands of his troops.