Source: TVLine
The final conflict with the Army of the 12 Monkeys begins when the Witness returns to Project Splinter.
Episode 4.02 - Ouroboros
Travelers come face to face with ghosts from their past when they find themselves maneuvering around their own timelines.
Episode 4.03 - 45 RPM
Cassie travels back in time to confront a younger Olivia; Cole helps Jennifer find the meaning behind her final Primary vision.