In the lab scene, the protagonist meets Barbara, who explains the concept of time inversion. The lab is a secure facility, likely tied to TENET, where the protagonist is introduced to inverted objects, specifically bullets that move backward through time. Barbara demonstrates this by having him "catch" an inverted bullet, explaining that time inversion is achieved by manipulating the entropy of objects.

This meeting is essential to the protagonist’s understanding of the physics behind inversion, marking the start of his journey into this time-bending world. Barbara also hints at the global-scale implications of this technology, preparing the protagonist for the mission ahead.